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Atari ST Machine Specific Programming In Assembly Chapter 11: Reconstructing Source Files There are four legitimate sources for software. You can purchase it, you can find it in magazines and books, you can obtain it free as public domain or you can write it yourself. Rarely will you be satisfied with any of it. Software that you write is easy to alter because you have the source program. Magazines and books usually provide source programs also. But commercial and public domain software rarely, if ever, provide that convenience. Altering programs for which you do not have the source program is difficult, but not impossible. The task is addressed in this chapter. Learning From Other Programmers If you are a new programmer, you may not realize the extent to which experienced programmers study code produced by other programmers. Of course, you will read in your references that the only way to become a programmer is to write programs. To the extent that writing programs is the only way in which you can test your accumulation of knowledge about programming, that statement is true. But it is not the whole story. I don't think that I can be contradicted in the least when I say that you will learn more about programming by studying programs produced by other programmers than you ever will by working alone. I am convinced of that because I am convinced that the accumulation of knowledge and ability is regenerative, in the electronic sense; that is, you learn a little from someone, apply that to what you already know and use that combined knowledge to generate new knowledge by your own initiative. Then you initiate the cycle again by learning a little from someone else. I am not striving to impress you with some radical new concept here; I am constructing an argument concerning our debt to each other. The conclusion of that argument is this: no one has ever learned anything in solitude. We all learn from each other; therefore, no one owns knowledge. To the extent that every idea we can possibly conceive is based on knowledge contributed by others, no idea, however original can stand isolated; therefore, every item of work that we produce is inherently public domain to some degree, whether we admit the fact and regardless of our feelings about the matter. But, because I want to illustrate the alteration of programs produced by third party programmers; that is, programs not produced by you nor me; I am forced to consider the feelings and opinions of those programmers. I want to assure those programmers and you that my intent is not to provide you with assistance in pirating or plagiarizing their works. With no malice intended, I only suggest that after you have purchased software you have the right to study and alter it for your own use if you choose to do so. Furthermore, I suggest that, unless you attempt to unethically exploit that right by selling or giving away copies of either the original works or altered versions, the authors and distributors of those works lose nothing by your study and alterations, and, in fact, invite such activities merely by making the material available. If I design a program or write a book that I don't want you to study or alter, then I would be foolish to publish either. Imagine the difficulties that publishers would encounter if they were to try to prevent readers from revealing the contents of magazines and books to those who had not purchased and read them. One final point, then we'll get down to the business at hand. Software producers have asked that purchasers help to protect them against piracy. I would be more sympathetic to that plea if software developers, in turn, would help to protect purchasers from software that does not perform as specified and from expensive upgrades that introduce more errors than are corrected; would write manuals for their products which actually explained their use; and, finally, would provide the source code so that users could correct the errors that seem beyond the ability of the developers. From Machine Language to Source Program As a first example, I will step you through the process of converting the machine language of PRG_8AR.ACC, introduced in chapter 10, to a source program that may be altered and assembled. The process involves the use of the AssemPro debugger to provide disassembly and reassembly listings of the object program. A few things to remember are: 1. The disassembly and reassembly AssemPro functions are rather unforgiving. Any errors in usage are apt to cause system crashes. 2. The listings provided by these functions are saved to the directory from which the object program is loaded; therefore, make sure that there is room before you begin. 3. Tiny programs produce large listings; large programs produce extremely large listings. Examples will be given. 4. The listings provided may contain characters that are not printer compatible. These must be removed before hardcopy is feasible. During the machine language to assembly language conversion process you may find it necessary to reload the object program in order to single step through a portion of the program or to obtain a fresh disassembly or reassembly listing. To insure that the initial disassembly will be reproducible, you must be able to load and reload the object program into a reproducible environment. This means that all accessories and auto executed programs contained in the system environment during initial disassembly and/or reassembly must reside within the environment during subsequent disassemblies and/or reassemblies. Furthermore, no other programs should be executed before using AssemPro to disassemble your object code. In fact, you may find it necessary to cold boot the system between subsequent disassemblies of one object program. The point is that you will want the addresses shown on all listings to be identical; therefore, you must insure that the object program will be loaded into the same area of memory each time. Begin by executing AssemPro. From the debugger, click on the Execute program button. When the dialog box appears, click on the OK button. From the file selector choose PRG_8AR.ACC. Remember that the disassembly and reassembly listings will be saved to the directory from which the program is loaded into the debugger. Always allow sufficient room for the listings. For example, PRG_8AR.ACC occupies only 1082 bytes of disk space, but the disassembly listing requires 15,881 bytes and the reassembly listing requires 17,074 bytes. At those ratios, a program that requires 30K to 40K bytes of disk space may produce listings that require as much as 500K bytes of space. After the program has been loaded into the debugger, record the program's start address. I will be using the values obtained on my machine so that you will be able to observe the addresses and calculations involved. The starting address for my example is $B20F0. Click on the from address button. On the line which appears at the bottom of the debugger screen, type the address of the program's basepage. That address is Start address minus $100; for this example it is $B20F0 - $100 = $B1FF0. Refer to page 97 of the COMPUTE! TOS book and figure 11.1 during the discussion to follow. Figure 11.1. PRG_8AR.ACC's basepage as it appears in the AssemPro debugger output window. The longword stored at the first address of the basepage is just the first address of the basepage itself; that is, $000B1FF0 is stored at $0B1FF0. The longword stored at basepage address + 8 ($0B1FF8) is the program's start address, $000B20F0. This address is also called the text segment address. The longword stored at basepage address + 12 ($0B1FFC) is the length of the program's text segment, $000001E8. The longword stored at basepage address + 16 ($0B2000) is the address of the program's data segment, $000B22D8. The longword stored at basepage address + 20 ($0B2004) is the length of the program's data segment, $0000021C. The longword stored at basepage address + 24 ($0B2008) is the address of the program's bss segment, $000B24F4. The longword stored at basepage address + 28 ($0B200C) is the length of the program's bss segment, $00000552. We want disassembly and reassembly listings that begin at the program's start address, called the "from address" by AssemPro, and terminate at the end of the longword following the end of the program, called the "to address" by AssemPro. The from address is given; it is $B20F0. The to address must be calculated; it is the sum of the program's bss address plus the length of the bss segment plus 4; that is, $B24F4 + $552 + $4 = $B2A4A. Figure 11.2 illustrates the appearance of the Disassembling dialog box just before the OK button is pressed; figure 11.3 is the disassembly listing. Note: there will be times when you will want to exclude a program's bss section from a disassembly listing because of its extreme length. In fact, the bss section reveals little information beyond the amount of memory reserved for the data to be stored there. Here I have simply omitted a large repetitious segment of the listing. Figure 11.2. Preparing the Disassembling dialog box. From the Debugger menu, click on the Disassembling option. Type the from address and the to address on the appropriate lines. Click on File: and type the name to be assigned to the listing file. On the heading line, type an appropriate heading for the listing. Click on the continuous button, and make sure that the hexadecimal button is highlighted; click on the button if it is not. Finally, click on the OK button. A flag will appear in place of the mouse arrow, and it will remain until the disassembly is complete. Figure 11.3. The disassembly listing. PRG_8AR.ACC Disassembly 0B20F0 4FFA0954 LEA $B2A46(PC),A7 0B20F4 3F3C0000 MOVE.W #0,-(A7) 0B20F8 487A03E5 PEA $B24DF(PC) 0B20FC 3F3C003C MOVE.W #$3C,-(A7) 0B2100 4E41 TRAP #1 0B2102 508F ADDQ.L #8,A7 0B2104 33C0000B2530 MOVE.W D0,$B2530 0B210A 3F3A0424 MOVE.W $B2530(PC),-(A7) 0B210E 3F3C0001 MOVE.W #1,-(A7) 0B2112 3F3C0046 MOVE.W #$46,-(A7) 0B2116 4E41 TRAP #1 0B2118 5C8F ADDQ.L #6,A7 0B211A 363C00C8 MOVE.W #$C8,D3 0B211E 4BFA01B8 LEA $B22D8(PC),A5 0B2122 49FA03D0 LEA $B24F4(PC),A4 0B2126 47FA02E3 LEA $B240B(PC),A3 0B212A 610000DE BSR $B220A 0B212E 38BC000A MOVE.W #$A,(A4) 0B2132 397C00000002 MOVE.W #0,2(A4) 0B2138 397C00010004 MOVE.W #1,4(A4) 0B213E 397C00000006 MOVE.W #0,6(A4) 0B2144 397C00000008 MOVE.W #0,8(A4) 0B214A 61000178 BSR $B22C4 0B214E 610000BA BSR $B220A 0B2152 38BC0023 MOVE.W #$23,(A4) 0B2156 397C00010002 MOVE.W #1,2(A4) 0B215C 397C00010004 MOVE.W #1,4(A4) 0B2162 397C00010006 MOVE.W #1,6(A4) 0B2168 397C00000008 MOVE.W #0,8(A4) 0B216E 41FA038E LEA $B24FE(PC),A0 0B2172 33E80004000B2508 MOVE.W 4(A0),$B2508 0B217A 23FC000B24CB000B251C MOVE.L #$B24CB,$B251C 0B2184 6100013E BSR $B22C4 0B2188 33FA0388000B2544 MOVE.W $B2512(PC),$B2544 0B2190 61000078 BSR $B220A 0B2194 23FC000B2534000B251C MOVE.L #$B2534,$B251C 0B219E 38BC0017 MOVE.W #$17,(A4) 0B21A2 397C00000002 MOVE.W #0,2(A4) 0B21A8 397C00010004 MOVE.W #1,4(A4) 0B21AE 397C00010006 MOVE.W #1,6(A4) 0B21B4 397C00000008 MOVE.W #0,8(A4) 0B21BA 61000108 BSR $B22C4 0B21BE 41FA0374 LEA $B2534(PC),A0 0B21C2 0C500028 CMPI.W #$28,(A0) 0B21C6 66D6 BNE.S $B219E 0B21C8 30280008 MOVE.W 8(A0),D0 0B21CC B07A0376 CMP.W $B2544(PC),D0 0B21D0 66CC BNE.S $B219E 0B21D2 0C790005000B2532 CMPI.W #5,$B2532 0B21DA 67C2 BEQ.S $B219E 0B21DC 6100002C BSR $B220A 0B21E0 0C790005000B2532 CMPI.W #5,$B2532 0B21E8 6702 BEQ.S $B21EC 0B21EA 60B2 BRA.S $B219E 0B21EC 3F3A0342 MOVE.W $B2530(PC),-(A7) 0B21F0 3F3C003E MOVE.W #$3E,-(A7) 0B21F4 4E41 TRAP #1 0B21F6 588F ADDQ.L #4,A7 0B21F8 3F3C0001 MOVE.W #1,-(A7) 0B21FC 3F3A0332 MOVE.W $B2530(PC),-(A7) 0B2200 3F3C0046 MOVE.W #$46,-(A7) 0B2204 4E41 TRAP #1 0B2206 5C8F ADDQ.L #6,A7 0B2208 6094 BRA.S $B219E 0B220A 41FA020F LEA $B241B(PC),A0 0B220E 610000BC BSR $B22CC 0B2212 41FA00DC LEA $B22F0(PC),A0 0B2216 303A031A MOVE.W $B2532(PC),D0 0B221A E548 LSL.W #2,D0 0B221C 20700000 MOVEA.L 0(A0,D0.W),A0 0B2220 610000AA BSR $B22CC 0B2224 41FA0295 LEA $B24BB(PC),A0 0B2228 610000A2 BSR $B22CC 0B222C 41FA021D LEA $B244B(PC),A0 0B2230 6100009A BSR $B22CC 0B2234 41FA0285 LEA $B24BB(PC),A0 0B2238 61000092 BSR $B22CC 0B223C 41FA0245 LEA $B2483(PC),A0 0B2240 6100008A BSR $B22CC 0B2244 7E00 MOVEQ #0,D7 0B2246 7C04 MOVEQ #4,D6 0B2248 41FA02FC LEA $B2546(PC),A0 0B224C 2C4D MOVEA.L A5,A6 0B224E 3A3C0005 MOVE.W #5,D5 0B2252 303C000B MOVE.W #$B,D0 0B2256 10FC0020 MOVE.B #$20,(A0)+ 0B225A 51C8FFFA DBRA D0,$B2256 0B225E 3007 MOVE.W D7,D0 0B2260 0200000F ANDI.B #$F,D0 0B2264 10330000 MOVE.B 0(A3,D0.W),D0 0B2268 10C0 MOVE.B D0,(A0)+ 0B226A 10FC003A MOVE.B #$3A,(A0)+ 0B226E 10FC0020 MOVE.B #$20,(A0)+ 0B2272 3007 MOVE.W D7,D0 0B2274 E348 LSL.W #1,D0 0B2276 225E MOVEA.L (A6)+,A1 0B2278 30310000 MOVE.W 0(A1,D0.W),D0 0B227C 7403 MOVEQ #3,D2 0B227E E958 ROL.W #4,D0 0B2280 1200 MOVE.B D0,D1 0B2282 0201000F ANDI.B #$F,D1 0B2286 4881 EXT.W D1 0B2288 12331000 MOVE.B 0(A3,D1.W),D1 0B228C 10C1 MOVE.B D1,(A0)+ 0B228E 51CAFFEE DBRA D2,$B227E 0B2292 10FC0020 MOVE.B #$20,(A0)+ 0B2296 10FC0020 MOVE.B #$20,(A0)+ 0B229A 51CDFFC2 DBRA D5,$B225E 0B229E 10BC0000 MOVE.B #0,(A0) 0B22A2 41FA02A2 LEA $B2546(PC),A0 0B22A6 61000024 BSR $B22CC 0B22AA 41FA016F LEA $B241B(PC),A0 0B22AE 6100001C BSR $B22CC 0B22B2 06470001 ADDI.W #1,D7 0B22B6 51CEFF90 DBRA D6,$B2248 0B22BA 06790001000B2532 ADDI.W #1,$B2532 0B22C2 4E75 RTS 0B22C4 220D MOVE.L A5,D1 0B22C6 3003 MOVE.W D3,D0 0B22C8 4E42 TRAP #2 0B22CA 4E75 RTS 0B22CC 2F08 MOVE.L A0,-(A7) 0B22CE 3F3C0009 MOVE.W #9,-(A7) 0B22D2 4E41 TRAP #1 0B22D4 5C8F ADDQ.L #6,A7 0B22D6 4E75 RTS 0B22D8 000B DC.W $B 0B22DA 24F4000B MOVE.L $B(A4,D0.W),(A2)+ 0B22DE 24FE MOVE.L SR,(A2)+ 0B22E0 000B DC.W $B 0B22E2 2508 MOVE.L A0,-(A2) 0B22E4 000B DC.W $B 0B22E6 2512 MOVE.L (A2),-(A2) 0B22E8 000B DC.W $B 0B22EA 251C MOVE.L (A4)+,-(A2) 0B22EC 000B DC.W $B 0B22EE 2526 MOVE.L -(A6),-(A2) 0B22F0 000B DC.W $B 0B22F2 2304 MOVE.L D4,-(A1) 0B22F4 000B DC.W $B 0B22F6 2329000B MOVE.L $B(A1),-(A1) 0B22FA 2363000B MOVE.L -(A3),$B(A1) 0B22FE 239E000B MOVE.L (A6)+,$B(A1,D0.W) 0B2302 23D80D0A5445 MOVE.L (A0)+,$A5445 0B2308 5354 SUBQ.W #1,(A4) 0B230A 2050 MOVEA.L (A0),A0 0B230C 4F49 DC.W $4F49 ;"OI" 0B230E 4E542030 LINK A4,#$2030 0B2312 3A20 MOVE.W -(A0),D5 0B2314 4265 CLR.W -(A5) 0B2316 666F BNE.S $B2387 0B2318 7265 MOVEQ #$65,D1 0B231A 2061 MOVEA.L -(A1),A0 0B231C 7070 MOVEQ #$70,D0 0B231E 6C5F BGE.S $B237F 0B2320 696E BVS.S $B2390 0B2322 6974 BVS.S $B2398 0B2324 0D0A0D0A MOVEP.W $D0A(A2),D6 0B2328 000D DC.W $D 0B232A 0A544553 EORI.W #$4553,(A4) 0B232E 5420 ADDQ.B #2,-(A0) 0B2330 504F ADDQ.W #8,A7 0B2332 494E DC.W $494E ;"IN" 0B2334 5420 ADDQ.B #2,-(A0) 0B2336 313A2041 MOVE.W $B4379(PC),-(A0) 0B233A 6674 BNE.S $B23B0 0B233C 6572 BCS.S $B23B0 0B233E 2061 MOVEA.L -(A1),A0 0B2340 7070 MOVEQ #$70,D0 0B2342 6C5F BGE.S $B23A3 0B2344 696E BVS.S $B23B4 0B2346 6974 BVS.S $B23BC 0B2348 2C20 MOVE.L -(A0),D6 0B234A 6265 BHI.S $B23B1 0B234C 666F BNE.S $B23BD 0B234E 7265 MOVEQ #$65,D1 0B2350 206D656E MOVEA.L $656E(A5),A0 0B2354 755F DC.W $755F ;"u_" 0B2356 7265 MOVEQ #$65,D1 0B2358 6769 BEQ.S $B23C3 0B235A 7374 DC.W $7374 ;"st" 0B235C 6572 BCS.S $B23D0 0B235E 0D0A0D0A MOVEP.W $D0A(A2),D6 0B2362 000D DC.W $D 0B2364 0A544553 EORI.W #$4553,(A4) 0B2368 5420 ADDQ.B #2,-(A0) 0B236A 504F ADDQ.W #8,A7 0B236C 494E DC.W $494E ;"IN" 0B236E 5420 ADDQ.B #2,-(A0) 0B2370 323A2041 MOVE.W $B43B3(PC),D1 0B2374 6674 BNE.S $B23EA 0B2376 6572 BCS.S $B23EA 0B2378 206D656E MOVEA.L $656E(A5),A0 0B237C 755F DC.W $755F ;"u_" 0B237E 7265 MOVEQ #$65,D1 0B2380 6769 BEQ.S $B23EB 0B2382 7374 DC.W $7374 ;"st" 0B2384 6572 BCS.S $B23F8 0B2386 2C20 MOVE.L -(A0),D6 0B2388 6265 BHI.S $B23EF 0B238A 666F BNE.S $B23FB 0B238C 7265 MOVEQ #$65,D1 0B238E 2065 MOVEA.L -(A5),A0 0B2390 766E MOVEQ #$6E,D3 0B2392 745F MOVEQ #$5F,D2 0B2394 6D65 BLT.S $B23FB 0B2396 7361 DC.W $7361 ;"sa" 0B2398 670D BEQ.S $B23A7 0B239A 0A0D DC.W $A0D 0B239C 0A000D0A EORI.B #$A,D0 0B23A0 5445 ADDQ.W #2,D5 0B23A2 5354 SUBQ.W #1,(A4) 0B23A4 2050 MOVEA.L (A0),A0 0B23A6 4F49 DC.W $4F49 ;"OI" 0B23A8 4E542033 LINK A4,#$2033 0B23AC 3A20 MOVE.W -(A0),D5 0B23AE 496E DC.W $496E ;"In" 0B23B0 206D6573 MOVEA.L $6573(A5),A0 0B23B4 7361 DC.W $7361 ;"sa" 0B23B6 6765 BEQ.S $B241D 0B23B8 2068616E MOVEA.L $616E(A0),A0 0B23BC 646C BCC.S $B242A 0B23BE 6572 BCS.S $B2432 0B23C0 2C20 MOVE.L -(A0),D6 0B23C2 6265 BHI.S $B2429 0B23C4 666F BNE.S $B2435 0B23C6 7265 MOVEQ #$65,D1 0B23C8 2065 MOVEA.L -(A5),A0 0B23CA 766E MOVEQ #$6E,D3 0B23CC 745F MOVEQ #$5F,D2 0B23CE 6D65 BLT.S $B2435 0B23D0 7361 DC.W $7361 ;"sa" 0B23D2 670D BEQ.S $B23E1 0B23D4 0A0D DC.W $A0D 0B23D6 0A000D0A EORI.B #$A,D0 0B23DA 5445 ADDQ.W #2,D5 0B23DC 5354 SUBQ.W #1,(A4) 0B23DE 2050 MOVEA.L (A0),A0 0B23E0 4F49 DC.W $4F49 ;"OI" 0B23E2 4E542034 LINK A4,#$2034 0B23E6 3A20 MOVE.W -(A0),D5 0B23E8 496E DC.W $496E ;"In" 0B23EA 206D6573 MOVEA.L $6573(A5),A0 0B23EE 7361 DC.W $7361 ;"sa" 0B23F0 6765 BEQ.S $B2457 0B23F2 2068616E MOVEA.L $616E(A0),A0 0B23F6 646C BCC.S $B2464 0B23F8 6572 BCS.S $B246C 0B23FA 2073 DC.W $2073 ;" s" 0B23FC 6563 BCS.S $B2461 0B23FE 6F6E BLE.S $B246E 0B2400 6420 BCC.S $B2422 0B2402 7469 MOVEQ #$69,D2 0B2404 6D65 BLT.S $B246B 0B2406 0D0A0D0A MOVEP.W $D0A(A2),D6 0B240A 0030 DC.W $30 0B240C 3132 DC.W $3132 ;"12" 0B240E 3334 DC.W $3334 ;"34" 0B2410 3536 DC.W $3536 ;"56" 0B2412 37383941 MOVE.W $3941,-(A3) 0B2416 4243 CLR.W D3 0B2418 4445 NEG.W D5 0B241A 460D DC.W $460D 0B241C 0A002020 EORI.B #$20,D0 0B2420 2020 MOVE.L -(A0),D0 0B2422 2020 MOVE.L -(A0),D0 0B2424 2020 MOVE.L -(A0),D0 0B2426 2020 MOVE.L -(A0),D0 0B2428 2020 MOVE.L -(A0),D0 0B242A 2020 MOVE.L -(A0),D0 0B242C 2020 MOVE.L -(A0),D0 0B242E 2020 MOVE.L -(A0),D0 0B2430 2020 MOVE.L -(A0),D0 0B2432 2020 MOVE.L -(A0),D0 0B2434 2020 MOVE.L -(A0),D0 0B2436 2020 MOVE.L -(A0),D0 0B2438 2020 MOVE.L -(A0),D0 0B243A 2020 MOVE.L -(A0),D0 0B243C 2020 MOVE.L -(A0),D0 0B243E 4145 DC.W $4145 ;"AE" 0B2440 5320 SUBQ.B #1,-(A0) 0B2442 4152 DC.W $4152 ;"AR" 0B2444 5241 ADDQ.W #1,D1 0B2446 5953 SUBQ.W #4,(A3) 0B2448 0D0A0043 MOVEP.W $43(A2),D6 0B244C 4F4E DC.W $4F4E ;"ON" 0B244E 5452 ADDQ.W #2,(A2) 0B2450 4F4C DC.W $4F4C ;"OL" 0B2452 2020 MOVE.L -(A0),D0 0B2454 474C DC.W $474C ;"GL" 0B2456 4F42 DC.W $4F42 ;"OB" 0B2458 414C DC.W $414C ;"AL" 0B245A 2020 MOVE.L -(A0),D0 0B245C 2049 MOVEA.L A1,A0 0B245E 4E545F49 LINK A4,#$5F49 0B2462 4E20 DC.W $4E20 ;"N " 0B2464 2020 MOVE.L -(A0),D0 0B2466 494E DC.W $494E ;"IN" 0B2468 545F ADDQ.W #2,(A7)+ 0B246A 4F55 DC.W $4F55 ;"OU" 0B246C 5420 ADDQ.B #2,-(A0) 0B246E 2041 MOVEA.L D1,A0 0B2470 4444 NEG.W D4 0B2472 525F ADDQ.W #1,(A7)+ 0B2474 494E DC.W $494E ;"IN" 0B2476 2020 MOVE.L -(A0),D0 0B2478 4144 DC.W $4144 ;"AD" 0B247A 4452 NEG.W (A2) 0B247C 5F4F SUBQ.W #7,A7 0B247E 5554 SUBQ.W #2,(A4) 0B2480 0D0A002D MOVEP.W $2D(A2),D6 0B2484 2D2D2D2D MOVE.L $2D2D(A5),-(A6) 0B2488 2D2D2020 MOVE.L $2020(A5),-(A6) 0B248C 2D2D2D2D MOVE.L $2D2D(A5),-(A6) 0B2490 2D2D2D20 MOVE.L $2D20(A5),-(A6) 0B2494 202D2D2D MOVE.L $2D2D(A5),D0 0B2498 2D2D2D2D MOVE.L $2D2D(A5),-(A6) 0B249C 2020 MOVE.L -(A0),D0 0B249E 2D2D2D2D MOVE.L $2D2D(A5),-(A6) 0B24A2 2D2D2D20 MOVE.L $2D20(A5),-(A6) 0B24A6 202D2D2D MOVE.L $2D2D(A5),D0 0B24AA 2D2D2D2D MOVE.L $2D2D(A5),-(A6) 0B24AE 2020 MOVE.L -(A0),D0 0B24B0 2D2D2D2D MOVE.L $2D2D(A5),-(A6) 0B24B4 2D2D2D2D MOVE.L $2D2D(A5),-(A6) 0B24B8 0D0A0020 MOVEP.W $20(A2),D6 0B24BC 2020 MOVE.L -(A0),D0 0B24BE 2020 MOVE.L -(A0),D0 0B24C0 2020 MOVE.L -(A0),D0 0B24C2 2020 MOVE.L -(A0),D0 0B24C4 2020 MOVE.L -(A0),D0 0B24C6 2000 MOVE.L D0,D0 0B24C8 2020 MOVE.L -(A0),D0 0B24CA 00202041 ORI.B #$41,-(A0) 0B24CE 6363 BLS.S $B2533 0B24D0 6573 BCS.S $B2545 0B24D2 736F DC.W $736F ;"so" 0B24D4 7279 MOVEQ #$79,D1 0B24D6 2041 MOVEA.L D1,A0 0B24D8 7272 MOVEQ #$72,D1 0B24DA 6179 BSR.S $B2555 0B24DC 7320 DC.W $7320 ;"s " 0B24DE 00453A5C ORI.W #$3A5C,D5 0B24E2 5052 ADDQ.W #8,(A2) 0B24E4 475F DC.W $475F ;"G_" 0B24E6 385C MOVEA.W (A4)+,A4 0B24E8 5052 ADDQ.W #8,(A2) 0B24EA 475F DC.W $475F ;"G_" 0B24EC 3841 MOVEA.W D1,A4 0B24EE 522E4441 ADDQ.B #1,$4441(A6) 0B24F2 5400 ADDQ.B #2,D0 0B24F4 00000000 ORI.B #0,D0 The section containing addresses 0B24F8 - 0B2A40 omitted. 0B2A44 00000000 ORI.B #0,D0 0B2A48 00000000 ORI.B #0,D0 When the mouse arrow appears following disassembly, choose the Reassembling option from the debugger menu. Click on File: and change the extension from DSM to ASM. Click on the OK button. When the More Start Addresses dialog box appears, click on the Quit button. A flag will appear in place of the mouse arrow until the reassembly is complete. Figure 11.4 illustrates the appearance of the Reassembling dialog box just before you press the OK button; figure 11.5 is the reassembly listing, somewhat abbreviated, with the repetitious portion omitted. Figure 11.4. Preparing the reassembling dialog box. Preparing the File for Printing Before I place the reassembly listing in this document, I must remove certain characters that are not compatible with my printer. These are the characters following the semicolons on the lines 148 through 169. With TEMPUS, I remove the unwanted character groups by typing ;* on the Search below string: line, and by typing a blank space on the ... and replace by following line. I choose the whole text for the search region; start search at cursor, with the cursor at the semicolon of the first group; and selectable for the quantity option. When the START button is pressed, the cursor advances to each semicolon in turn, stopping to permit a selection from the Search & Replace selection dialog box. I can then choose YES, NO or CANCEL as desired. Figure 11.5. The reassembly listing. 1: K00001=0 2: K00003=$3C 3: K00004=1 4: K00006=$46 5: K00007=$C8 6: K0000C=$A 7: K0000D=2 8: K0000E=4 9: K0000F=6 10: K00010=8 11: K00012=$23 12: K0001A=$17 13: K0001B=$28 14: K0001D=5 15: K00020=$3E 16: K00028=$B 17: K00029=$20 18: K0002B=$F 19: K0002C=$3A 20: K0002D=3 21: K00031=9 22: LEA L00000(PC),A7 23: MOVE.W #K00001,-(A7) 24: PEA L00002+1(PC) 25: MOVE.W #K00003,-(A7) 26: TRAP #K00004 27: ADDQ.L #8,A7 28: MOVE.W D0,L00005 29: MOVE.W L00005(PC),-(A7) 30: MOVE.W #K00004,-(A7) 31: MOVE.W #K00006,-(A7) 32: TRAP #K00004 33: ADDQ.L #6,A7 34: MOVE.W #K00007,D3 35: LEA L00008(PC),A5 36: LEA L00009(PC),A4 37: LEA L0000A+1(PC),A3 38: BSR L0000B 39: MOVE.W #K0000C,(A4) 40: MOVE.W #K00001,K0000D(A4) 41: MOVE.W #K00004,K0000E(A4) 42: MOVE.W #K00001,K0000F(A4) 43: MOVE.W #K00001,K00010(A4) 44: BSR L00011 45: BSR L0000B 46: MOVE.W #K00012,(A4) 47: MOVE.W #K00004,K0000D(A4) 48: MOVE.W #K00004,K0000E(A4) 49: MOVE.W #K00004,K0000F(A4) 50: MOVE.W #K00001,K00010(A4) 51: LEA L00013(PC),A0 52: MOVE.W K0000E(A0),L00014 53: MOVE.L #L00015+1,L00016 54: BSR L00011 55: MOVE.W L00017(PC),L00018 56: BSR L0000B 57: MOVE.L #L00019,L00016 58: L0001C:MOVE.W #K0001A,(A4) 59: MOVE.W #K00001,K0000D(A4) 60: MOVE.W #K00004,K0000E(A4) 61: MOVE.W #K00004,K0000F(A4) 62: MOVE.W #K00001,K00010(A4) 63: BSR L00011 64: LEA L00019(PC),A0 65: CMPI.W #K0001B,(A0) 66: BNE.S L0001C 67: MOVE.W K00010(A0),D0 68: CMP.W L00018(PC),D0 69: BNE.S L0001C 70: CMPI.W #K0001D,L0001E 71: BEQ.S L0001C 72: BSR L0000B 73: CMPI.W #K0001D,L0001E 74: BEQ.S L0001F 75: BRA.S L0001C 76: L0001F:MOVE.W L00005(PC),-(A7) 77: MOVE.W #K00020,-(A7) 78: TRAP #K00004 79: ADDQ.L #4,A7 80: MOVE.W #K00004,-(A7) 81: MOVE.W L00005(PC),-(A7) 82: MOVE.W #K00006,-(A7) 83: TRAP #K00004 84: ADDQ.L #6,A7 85: BRA.S L0001C 86: L0000B:LEA L00021+1(PC),A0 87: BSR L00022 88: LEA L00023(PC),A0 89: MOVE.W L0001E(PC),D0 90: LSL.W #K0000D,D0 91: MOVEA.L K00001(A0,D0.W),A0 92: BSR L00022 93: LEA L00024+1(PC),A0 94: BSR L00022 95: LEA L00025+1(PC),A0 96: BSR L00022 97: LEA L00024+1(PC),A0 98: BSR L00022 99: LEA L00026+1(PC),A0 100: BSR L00022 101: MOVEQ #K00001,D7 102: MOVEQ #K0000E,D6 103: L00030:LEA L00027(PC),A0 104: MOVEA.L A5,A6 105: MOVE.W #K0001D,D5 106: MOVE.W #K00028,D0 107: L0002A:MOVE.B #K00029,(A0)+ 108: DBRA D0,L0002A 109: L0002F:MOVE.W D7,D0 110: ANDI.B #K0002B,D0 111: MOVE.B K00001(A3,D0.W),D0 112: MOVE.B D0,(A0)+ 113: MOVE.B #K0002C,(A0)+ 114: MOVE.B #K00029,(A0)+ 115: MOVE.W D7,D0 116: LSL.W #K00004,D0 117: MOVEA.L (A6)+,A1 118: MOVE.W K00001(A1,D0.W),D0 119: MOVEQ #K0002D,D2 120: L0002E:ROL.W #K0000E,D0 121: MOVE.B D0,D1 122: ANDI.B #K0002B,D1 123: EXT.W D1 124: MOVE.B K00001(A3,D1.W),D1 125: MOVE.B D1,(A0)+ 126: DBRA D2,L0002E 127: MOVE.B #K00029,(A0)+ 128: MOVE.B #K00029,(A0)+ 129: DBRA D5,L0002F 130: MOVE.B #K00001,(A0) 131: LEA L00027(PC),A0 132: BSR L00022 133: LEA L00021+1(PC),A0 134: BSR L00022 135: ADDI.W #K00004,D7 136: DBRA D6,L00030 137: ADDI.W #K00004,L0001E 138: RTS 139: L00011:MOVE.L A5,D1 140: MOVE.W D3,D0 141: TRAP #K0000D 142: RTS 143: L00022:MOVE.L A0,-(A7) 144: MOVE.W #K00031,-(A7) 145: TRAP #K00004 146: ADDQ.L #6,A7 147: RTS 148: L00008:DC.W K00028 149: DC.W $24F4 150: DC.W K00028 151: DC.W $24FE 152: DC.W K00028 153: DC.W $2508 154: DC.W K00028 155: DC.W $2512 156: DC.W K00028 157: DC.W $251C 158: DC.W K00028 159: DC.W $2526 160: L00023:DC.W K00028 161: DC.W $2304 162: DC.W K00028 163: DC.W $2329 164: DC.W K00028 165: DC.W $2363 166: DC.W K00028 167: DC.W $239E 168: DC.W K00028 169: DC.W $23D8 170: DC.W $D0A ;">CR<>LF<" 171: DC.W $5445 ;"TE" 172: DC.W $5354 ;"ST" 173: DC.W $2050 ;" P" 174: DC.W $4F49 ;"OI" 175: DC.W $4E54 ;"NT" 176: DC.W $2030 ;" 0" 177: DC.W $3A20 ;": " 178: DC.W $4265 ;"Be" 179: DC.W $666F ;"fo" 180: DC.W $7265 ;"re" 181: DC.W $2061 ;" a" 182: DC.W $7070 ;"pp" 183: DC.W $6C5F ;"l_" 184: DC.W $696E ;"in" 185: DC.W $6974 ;"it" 186: DC.W $D0A ;">CR<>LF<" 187: DC.W $D0A ;">CR<>LF<" 188: DC.W $D ;">0<>CR<" 189: DC.W $A54 ;">LF<T" 190: DC.W $4553 ;"ES" 191: DC.W $5420 ;"T " 192: DC.W $504F ;"PO" 193: DC.W $494E ;"IN" 194: DC.W $5420 ;"T " 195: DC.W $313A ;"1:" 196: DC.W $2041 ;" A" 197: DC.W $6674 ;"ft" 198: DC.W $6572 ;"er" 199: DC.W $2061 ;" a" 200: DC.W $7070 ;"pp" 201: DC.W $6C5F ;"l_" 202: DC.W $696E ;"in" 203: DC.W $6974 ;"it" 204: DC.W $2C20 ;", " 205: DC.W $6265 ;"be" 206: DC.W $666F ;"fo" 207: DC.W $7265 ;"re" 208: DC.W $206D ;" m" 209: DC.W $656E ;"en" 210: DC.W $755F ;"u_" 211: DC.W $7265 ;"re" 212: DC.W $6769 ;"gi" 213: DC.W $7374 ;"st" 214: DC.W $6572 ;"er" 215: DC.W $D0A ;">CR<>LF<" 216: DC.W $D0A ;">CR<>LF<" 217: DC.W $D ;">0<>CR<" 218: DC.W $A54 ;">LF<T" 219: DC.W $4553 ;"ES" 220: DC.W $5420 ;"T " 221: DC.W $504F ;"PO" 222: DC.W $494E ;"IN" 223: DC.W $5420 ;"T " 224: DC.W $323A ;"2:" 225: DC.W $2041 ;" A" 226: DC.W $6674 ;"ft" 227: DC.W $6572 ;"er" 228: DC.W $206D ;" m" 229: DC.W $656E ;"en" 230: DC.W $755F ;"u_" 231: DC.W $7265 ;"re" 232: DC.W $6769 ;"gi" 233: DC.W $7374 ;"st" 234: DC.W $6572 ;"er" 235: DC.W $2C20 ;", " 236: DC.W $6265 ;"be" 237: DC.W $666F ;"fo" 238: DC.W $7265 ;"re" 239: DC.W $2065 ;" e" 240: DC.W $766E ;"vn" 241: DC.W $745F ;"t_" 242: DC.W $6D65 ;"me" 243: DC.W $7361 ;"sa" 244: DC.W $670D ;"g>CR<" 245: DC.W $A0D ;">LF<>CR<" 246: DC.W $A00 ;">LF<>0<" 247: DC.W $D0A ;">CR<>LF<" 248: DC.W $5445 ;"TE" 249: DC.W $5354 ;"ST" 250: DC.W $2050 ;" P" 251: DC.W $4F49 ;"OI" 252: DC.W $4E54 ;"NT" 253: DC.W $2033 ;" 3" 254: DC.W $3A20 ;": " 255: DC.W $496E ;"In" 256: DC.W $206D ;" m" 257: DC.W $6573 ;"es" 258: DC.W $7361 ;"sa" 259: DC.W $6765 ;"ge" 260: DC.W $2068 ;" h" 261: DC.W $616E ;"an" 262: DC.W $646C ;"dl" 263: DC.W $6572 ;"er" 264: DC.W $2C20 ;", " 265: DC.W $6265 ;"be" 266: DC.W $666F ;"fo" 267: DC.W $7265 ;"re" 268: DC.W $2065 ;" e" 269: DC.W $766E ;"vn" 270: DC.W $745F ;"t_" 271: DC.W $6D65 ;"me" 272: DC.W $7361 ;"sa" 273: DC.W $670D ;"g>CR<" 274: DC.W $A0D ;">LF<>CR<" 275: DC.W $A00 ;">LF<>0<" 276: DC.W $D0A ;">CR<>LF<" 277: DC.W $5445 ;"TE" 278: DC.W $5354 ;"ST" 279: DC.W $2050 ;" P" 280: DC.W $4F49 ;"OI" 281: DC.W $4E54 ;"NT" 282: DC.W $2034 ;" 4" 283: DC.W $3A20 ;": " 284: DC.W $496E ;"In" 285: DC.W $206D ;" m" 286: DC.W $6573 ;"es" 287: DC.W $7361 ;"sa" 288: DC.W $6765 ;"ge" 289: DC.W $2068 ;" h" 290: DC.W $616E ;"an" 291: DC.W $646C ;"dl" 292: DC.W $6572 ;"er" 293: DC.W $2073 ;" s" 294: DC.W $6563 ;"ec" 295: DC.W $6F6E ;"on" 296: DC.W $6420 ;"d " 297: DC.W $7469 ;"ti" 298: DC.W $6D65 ;"me" 299: DC.W $D0A ;">CR<>LF<" 300: DC.W $D0A ;">CR<>LF<" 301: L0000A:DC.W $30 ;">0<0" 302: DC.W $3132 ;"12" 303: DC.W $3334 ;"34" 304: DC.W $3536 ;"56" 305: DC.W $3738 ;"78" 306: DC.W $3941 ;"9A" 307: DC.W $4243 ;"BC" 308: DC.W $4445 ;"DE" 309: L00021:DC.W $460D ;"F>CR<" 310: DC.W $A00 ;">LF<>0<" 311: DC.W $2020 ;" " 312: DC.W $2020 ;" " 313: DC.W $2020 ;" " 314: DC.W $2020 ;" " 315: DC.W $2020 ;" " 316: DC.W $2020 ;" " 317: DC.W $2020 ;" " 318: DC.W $2020 ;" " 319: DC.W $2020 ;" " 320: DC.W $2020 ;" " 321: DC.W $2020 ;" " 322: DC.W $2020 ;" " 323: DC.W $2020 ;" " 324: DC.W $2020 ;" " 325: DC.W $2020 ;" " 326: DC.W $2020 ;" " 327: DC.W $4145 ;"AE" 328: DC.W $5320 ;"S " 329: DC.W $4152 ;"AR" 330: DC.W $5241 ;"RA" 331: DC.W $5953 ;"YS" 332: DC.W $D0A ;">CR<>LF<" 333: L00025:DC.W $43 ;">0<C" 334: DC.W $4F4E ;"ON" 335: DC.W $5452 ;"TR" 336: DC.W $4F4C ;"OL" 337: DC.W $2020 ;" " 338: DC.W $474C ;"GL" 339: DC.W $4F42 ;"OB" 340: DC.W $414C ;"AL" 341: DC.W $2020 ;" " 342: DC.W $2049 ;" I" 343: DC.W $4E54 ;"NT" 344: DC.W $5F49 ;"_I" 345: DC.W $4E20 ;"N " 346: DC.W $2020 ;" " 347: DC.W $494E ;"IN" 348: DC.W $545F ;"T_" 349: DC.W $4F55 ;"OU" 350: DC.W $5420 ;"T " 351: DC.W $2041 ;" A" 352: DC.W $4444 ;"DD" 353: DC.W $525F ;"R_" 354: DC.W $494E ;"IN" 355: DC.W $2020 ;" " 356: DC.W $4144 ;"AD" 357: DC.W $4452 ;"DR" 358: DC.W $5F4F ;"_O" 359: DC.W $5554 ;"UT" 360: DC.W $D0A ;">CR<>LF<" 361: L00026:DC.W $2D ;">0<-" 362: DC.W $2D2D ;"--" 363: DC.W $2D2D ;"--" 364: DC.W $2D2D ;"--" 365: DC.W $2020 ;" " 366: DC.W $2D2D ;"--" 367: DC.W $2D2D ;"--" 368: DC.W $2D2D ;"--" 369: DC.W $2D20 ;"- " 370: DC.W $202D ;" -" 371: DC.W $2D2D ;"--" 372: DC.W $2D2D ;"--" 373: DC.W $2D2D ;"--" 374: DC.W $2020 ;" " 375: DC.W $2D2D ;"--" 376: DC.W $2D2D ;"--" 377: DC.W $2D2D ;"--" 378: DC.W $2D20 ;"- " 379: DC.W $202D ;" -" 380: DC.W $2D2D ;"--" 381: DC.W $2D2D ;"--" 382: DC.W $2D2D ;"--" 383: DC.W $2020 ;" " 384: DC.W $2D2D ;"--" 385: DC.W $2D2D ;"--" 386: DC.W $2D2D ;"--" 387: DC.W $2D2D ;"--" 388: DC.W $D0A ;">CR<>LF<" 389: L00024:DC.W K00029 ;">0< " 390: DC.W $2020 ;" " 391: DC.W $2020 ;" " 392: DC.W $2020 ;" " 393: DC.W $2020 ;" " 394: DC.W $2020 ;" " 395: DC.W $2000 ;" >0<" 396: DC.W $2020 ;" " 397: L00015:DC.W K00029 ;">0< " 398: DC.W $2041 ;" A" 399: DC.W $6363 ;"cc" 400: DC.W $6573 ;"es" 401: DC.W $736F ;"so" 402: DC.W $7279 ;"ry" 403: DC.W $2041 ;" A" 404: DC.W $7272 ;"rr" 405: DC.W $6179 ;"ay" 406: DC.W $7320 ;"s " 407: L00002:DC.W $45 ;">0<E" 408: DC.W $3A5C ;":\" 409: DC.W $5052 ;"PR" 410: DC.W $475F ;"G_" 411: DC.W $385C ;"8\" 412: DC.W $5052 ;"PR" 413: DC.W $475F ;"G_" 414: DC.W $3841 ;"8A" 415: DC.W $522E ;"R." 416: DC.W $4441 ;"DA" 417: DC.W $5400 ;"T>0<" 418: L00009:DC.W K00001 419: DC.W K00001 420: DC.W K00001 421: DC.W K00001 422: DC.W K00001 423: L00013:DC.W K00001 424: DC.W K00001 425: DC.W K00001 426: DC.W K00001 427: DC.W K00001 428: L00014:DC.W K00001 429: DC.W K00001 430: DC.W K00001 431: DC.W K00001 432: DC.W K00001 433: L00017:DC.W K00001 434: DC.W K00001 435: DC.W K00001 436: DC.W K00001 437: DC.W K00001 438: L00016:DC.W K00001 439: DC.W K00001 440: DC.W K00001 441: DC.W K00001 442: DC.W K00001 443: DC.W K00001 444: DC.W K00001 445: DC.W K00001 446: DC.W K00001 447: DC.W K00001 448: L00005:DC.W K00001 449: L0001E:DC.W K00001 450: L00019:DC.W K00001 451: DC.W K00001 452: DC.W K00001 453: DC.W K00001 454: DC.W K00001 455: DC.W K00001 456: DC.W K00001 457: DC.W K00001 458: L00018:DC.W K00001 459: L00027:DC.W K00001 460: DC.W K00001 Lines 461 - 1097 omitted to conserve space. 1098: DC.W K00001 1099: L00000:DC.W K00001 1100: DC.W K00001 1101: END If you have the TEMPUS editor, you should exit AssemPro and load the disassembly file into one window, then load the reassembly file into another. Then you can choose the underneath option to observe both files simultaneously. Alternately, you can use a word processor such as 1st Word Plus; otherwise, you will have to work with the files individually, but I intend to proceed with the discussion as if you are able to view both files simultaneously. Do not attempt to print either of the files on your printer yet. Compressing the Reassembly Listing The particular example that I am using provides a reassembly listing that is easily reworked. Other programs do not. Regardless of the its condition, the reassembly listing is usually the one that is altered so that it becomes a source program; however, the disassembly listing provides visual information that is sometimes obscured in the reassembly listing. As an example of the difference in information content of the listings, notice that virtually every number in the reassembly listing has been replaced by a constant identifier. We must change every one of those back to the original numbers so that we can see what it is that the program does. We can do that as we go along, or we can replace them all at once with the editor's replace function. Initially, I prefer to make changes individually until I know it is safe to perform a mass replace. Notice also that most of the addresses in the reassembly listing have been converted to labels. There is a list of the constant identifiers and their values at the beginning of the reassembly listing, but it is sometimes easier to refer to the disassembly listing to obtain those values. As the first instruction in the reassembly listing, you can see that the address of label L00000 is being loaded into register A7. That means, of course, that L00000 is the AssemPro generated label for the stack. If you run down the listing to L00000, you will see that it is the last label in the program, and you will see that it is preceded by a long list of DC.W K00001 pseudo ops. If you now run up to the K00001 declaration at the top of the listing, you will see that K00001 is the identifier for the quantity 0. Now run back down to L00000, then carefully run back up to the next label, which is L00027. All of the DC.W 0 pseudo ops between L00027 and L00000 are bss declarations in the original program. Unfortunately, AssemPro does not differentiate between data and bss declarations when it generates the reassembly listing. But that's ok; we can find out where we are by referring to the disassembly listing and the information in the basepage. Now, what we don't know is how many of those DC.W 0 declarations belong to L00027 and how many belong to L00000. That's ok too, because it doesn't matter; in the source program, the space reserved was only cosmetically separated. The declarations in the original program would have had to have been similar to that shown below. L00027: ds.l xxx ds.l yyy L00000: ds.l zzz where the space reserved by xxx and that reserved by yyy would have been inseparable anyway. All that we need is the total space reserved in the original program. That can be calculated thus: L00027 is at line number 459 in the listing, and there is a DC.W 0 declared there; L00000 is at line number 1099 in the listing, and there is a DC.W 0 declared there also, but we don't count that one--we only want those declared from L00027 to L00000 (Refer to the model above. We desire the sum of xxx and yyy.). Subtracting 459 from 1099 yields 640 (that's declared words), which is 320 longwords. Since we don't know what portion of this declaration to allocate to each label, and since it doesn't matter anyway, we can just split the amount between them, and we can delete all of the DC.W K00001 declarations from L00027 to L00000. And since we can determine that there are no other references to the label L00000 within the program simply by searching for that label, we can change the reference in the first instruction and the label itself to stack. After the alteration, the declarations would appear as shown below. L00027: ds.l 160 ds.l 160 stack: ds.l 1 Notice that I use lower case letters to indicate items which have been altered. Notice also that I have declared a single longword at the stack label, as is indicated in the reassembly listing, even though we know that in the original program ds.l 0 was used. That can always be changed later if to do so is desirable. Finally, notice that we have reduced the number of lines in the listing from 1101 to 462. If we had no hint about the output of the program, we could simply return to the top of the listing and begin to decipher instructions linearly. But we are able to execute the program and obtain output in a file. Furthermore, we know that the program is a desk accessory, so we know a great deal about the types of instructions within the text segment and something about the declarations in the data segment. With all of this knowledge, and with the help of the ASCII characters that are present, we can begin to reconstruct the data segment of the program. That activity will permit the most rapid reduction in listing size. As you run up the listing from L00027, past L0000A, to label L00023, notice that there are no labels at locations we might expect them to be if we refer to the original listing in chapter 10. That's because the labels zero, one, two, three and four were referenced indirectly within the program. Their locations were stored in pointer array test_header, and the address of test_header was stored in an address register. Without knowledge of the original listing, we would discover that as we work through the conversion. Still, we can work with the data declarations and insert the labels as we discover their locations. Starting at line 170 of the listing and continuing through line 417, referring to the program's output and to an ASCII table when necessary, we reconstruct the data section as shown in the listing in figure 11.6. We can assume that the carriage return/linefeed declared at line 170 is part of the declaration at line 171 because there is no null character between the two lines. At line 188, you can see how the null character would be declared; there, note the ">0<>CR<" following the semicolon. The >0< indicates the null character. The $D for the carriage return follows the null character at that location. The CR, LF and T mark the beginning of a new declaration. Figure 11.6. Partially reconstructed data section. dc.b $D,$A,'TEST POINT 0: Before appl_init',$D,$A,$D,$A,0 dc.b $D,$A,'TEST POINT 1: After appl_init, before menu_register',$D,$A,$D,$A,0 dc.b $D,$A,'TEST POINT 2: After menu_register, before evnt_mesag',$D,$A,$D,$A,0 dc.b $D,$A,'TEST POINT 3: In message handler, before evnt_mesag',$D,$A,$D,$A,0 dc.b $D,$A,'TEST POINT 4: In message handler second time',$D,$A,$D,$A,0 L0000A: dc.b '0123456789ABCDEF' L00021+1: dc.b $D,$A,0 dc.b ' AES ARRAYS',$D,$A,0 L00025+1: dc.b 'CONTROL GLOBAL INT_IN INT_OUT ADDR_IN ADDR_OUT',$D,$A,0 L00026+1 dc.b '_______ ______ ______ _______ _______ ________',$D,$A,0 L00024+1: dc.b ' ',$D,$A,0 dc.b ' ',$D,$A,0 L00015+1: dc.b ' Accessory Arrays ',0 L00002+1: dc.b 'E:\PRG_8\PRG_8AR.DAT',0 As we reconstruct the data segment of the program, we use dc.b pseudo ops to declare strings, not the dc.w pseudo ops. At line 309, note that the character F, which is part of the declaration above L00021, has been combined with the declaration at L00021. This occurred because a null character was not placed after the hex_table string in the original program (Remember the assumption made in the paragraph above--it could be wrong.). This fact would become evident as we work through the reassembly listing because there are no references to L00021 within the listing, but L00021+1 is referenced. You can verify this by searching through the listing for references to L00021. An explanation is provided in the last paragraph on page 105 of the AssemPro manual. The Label+1 phenomenon occurs whenever AssemPro must create a label at an odd address. We can handle this by changing L00021 to L00021+1 at line 309 and by placing the F character in the string to which it belongs. Concerning the hex string declaration, the pseudo op at line 301 is L0000A:DC.W $30 ;">0<0". This declares a null character followed by a 0. If we take the time to search for references to L0000A within the listing, we find that there are none. But L0000A+1 is referenced at line 37. There, the address of the table is loaded into A3. We can easily infer that an adjustment is in order. We can change the L0000A+1 to L0000A and declare the table as it should be. As it is with L00021, there is no direct reference to L00025, but L00025+1 is referenced, so we handle line 333 as we did line 309. L00026 at line 361 is changed to L00026+1. At line 389, L00024 is changed to L00024+1; and note that the constant K00029 at that location is just $20, the ASCII code for a space. Note also that a null character precedes the space. At line 396 two spaces are declared, following the null on line 395, and preceding the null on line 396. The space following the null on line 396 is part of the L00015+1 declaration " Accessory Arrays ". L00002 at line 407 must be changed to L00002+1, and we readily observe a file name and directory path at that location. We can now begin converting statements from the top of the listing, using the disassembly listing and the list of constant identifiers to fill in numeric values, and referring to the appropriate reference books to identify functions. The most prominent candidates for immediate conversion are the trap numbers. At each TRAP word, simply exchange the constant identifier for the constant itself. Then, at each location of a trap invocation, replace all constant identifiers with constants. As each function is identified, replace the appropriate label references within the invocation and at their site if possible. Above each function invocation, place a suitable label to describe the function. After doing this for the first two functions, they would appear as shown in figure 11.7. Figure 11.7. First two functions of the listing. create_file: lea stack(pc), sp move.w #0, -(sp) pea filename(pc) move.w #$3C, -(sp) trap #1 addq.l #8, sp move.w d0, file_handle redirect_output: move.w file_handle(pc), -(sp) move.w #1, -(sp) move.w #$46, -(sp) trap #1 addq.l #6, sp As the alterations shown in figure 11.7 are made, L00002+1 must be changed to filename at the label's site, as must L00005 be changed to file_handle. As we are making the file_handle exchange for L00005, we should notice that the program can be improved by pushing d0 onto the stack in the redirect_output function instead of pushing the variable file_handle, as was done in the original program; but, at this time, we should simply place a note in the listing to which attention can be directed later. We want to suppress improvements until we have confirmed the accuracy of the machine language to assembly language conversion. Don't forget to declare the ds.w 1 at the file_handle label site. As the first two functions are being transformed, the labels that are replaced there and at the label sites must also be replaced at all referencing locations. That activity would lead to the transformation of the two functions that exist at the L0001F label site. Those two transformed functions are shown in figure 11.8. Don't forget to alter all references to L0001F when it is changed to close_file. Figure 11.8. Two more functions disclosed. beq.s close_file BRA.S L0001C close_file: move.w file_handle(pc), -(sp) move.w #$3E, -(sp) trap #1 addq.l #4, sp _redirect_output: move.w #1, -(sp) move.w file_handle(pc), -(sp) move.w #$46, -(sp) trap #1 addq.l #6, sp The two program statements following the functions shown in figure 11.8 will lead us to a trap #2 subroutine. The first statement stores $C8, the AES call number in register D3; the second statement stores the address of a label in A5. Searching for all references to A5, eventually leads us to L00011 at which the trap #2 invocation resides. The very structure of the subroutine identifies it as the AES call. Thus we are able to identify L00008 as the label for the aes_pb. And, when all of the constant identifiers residing just below the BSR L0000B statement are replaced by the respective constants; and after observing the BSR L00011 statement just below those replaced constants, we can be sure that the address of the label being loaded into register A4 must be that of the array control. Therefore, each BSR L00011 can be changed to bsr aes, each reference to L00008 can be changed to a reference to aes_pb and each reference to L00009 can be changed to a reference to control. Control can be declared as a five word array thus: ds.w 5. At this point, we are unable to clearly identify references to the other five AES structures within the reassembly listing; but we do know the order in which their addresses must be stored in the aes_pb structure; therefore, using the disassembly listing as a guide, we can obtain the address of aes_pb as that which is being loaded into A5 at line 16, and at that location we can obtain the addresses of the other structures. At those addresses we will be able to determine both the amount of space reserved for each array and the relative positions of those declarations within the program. We then possess the required information to declare the structures within the reassembly listing. See figure 11.9, which shows the relevant parts of the disassembly listing. At address $B22D8, we can see the disassembly listing address of each of the structures in question. Figure 11.9. Relevant portions of the disassembly listing. 0B211A 363C00C8 MOVE.W #$C8,D3 0B211E 4BFA01B8 LEA $B22D8(PC),A5 0B2122 49FA03D0 LEA $B24F4(PC),A4 0B22D6 4E75 RTS 0B22D8 000B DC.W $B 0B22DA 24F4000B MOVE.L $B(A4,D0.W),(A2)+ 0B22DE 24FE MOVE.L SR,(A2)+ 0B22E0 000B DC.W $B 0B22E2 2508 MOVE.L A0,-(A2) 0B22E4 000B DC.W $B 0B22E6 2512 MOVE.L (A2),-(A2) 0B22E8 000B DC.W $B 0B22EA 251C MOVE.L (A4)+,-(A2) 0B22EC 000B DC.W $B 0B22EE 2526 MOVE.L -(A6),-(A2) 0B22F0 000B DC.W $B 0B22F2 2304 MOVE.L D4,-(A1) 0B22F4 000B DC.W $B 0B22F6 2329000B MOVE.L $B(A1),-(A1) 0B22FA 2363000B MOVE.L -(A3),$B(A1) 0B22FE 239E000B MOVE.L (A6)+,$B(A1,D0.W) 0B2302 23D80D0A5445 MOVE.L (A0)+,$A5445 Section omitted as unnecessary. 0B24F4 00000000 ORI.B #0,D0 0B24F8 00000000 ORI.B #0,D0 0B24FC 00000000 ORI.B #0,D0 0B2500 00000000 ORI.B #0,D0 0B2504 00000000 ORI.B #0,D0 0B2508 00000000 ORI.B #0,D0 0B250C 00000000 ORI.B #0,D0 0B2510 00000000 ORI.B #0,D0 0B2514 00000000 ORI.B #0,D0 0B2518 00000000 ORI.B #0,D0 0B251C 00000000 ORI.B #0,D0 0B2520 00000000 ORI.B #0,D0 0B2524 00000000 ORI.B #0,D0 0B2528 00000000 ORI.B #0,D0 0B252C 00000000 ORI.B #0,D0 0B2530 00000000 ORI.B #0,D0 0B2534 00000000 ORI.B #0,D0 0B2538 00000000 ORI.B #0,D0 0B253C 00000000 ORI.B #0,D0 0B2540 00000000 ORI.B #0,D0 0B2544 00000000 ORI.B #0,D0 0B2548 00000000 ORI.B #0,D0 Using the information in figure 11.9 we easily confirm that L00013 marks the declaration of the array global; and that L00014, L00017 and L00016 mark the declarations for int_in, int_out and addr_in. Notice that no label for addr_out appears in the reassembly listing. That's because the other structures were directly referenced within the program, but addr_out was not. As the labels for the referenced structures are altered, don't forget to change the label identifiers in the instructions which reference them. From figure 11.1, the image of a portion of the program's basepage, we can obtain the information needed to mark the data and bss seqments of the program. But that information is also pretty obvious from the layout of the reassembly and disassembly listings. Don't forget that the align statement is needed after those dc.b declarations. With the other AES structures identified, we are able to seek out the other AES function invocations, and with a knowledge of the input requirements for those functions and their returns, we are able to identify the location of the menu text string, the message array and the variable menu_id. From the top of the listing again, the BSR L0000B instruction sends us to the statement which loads L00021+1 into A0. The BSR L00022 statement just below that sends us to a trap #1 invocation. Replacing the constant identifier there, K00031, with 9 readily identifies the function as GEMDOS c_conws, the print line function, and thereby, we realize that the contents of A0 must be the address of a string. We have, of course, already noted that the string declared at L00021+1 is a carriage return/linefeed combination; we can now choose to replace references to L00021+1 as references to the label newline, and references to L00022 as references to print_line. The five instructions below the branch to the print_line subroutine accomplish the following: 1. An address is loaded into A0. 2. A value is stored in D0; then the contents of D0 are multiplied by 4. 3. D0 is used as an index register in an address register indirect with index instruction to load a new address into A0. 4. The print_line subroutine is invoked to print a string. We conclude that L00023, the label identifying the address which is loaded into A0 in item 1, must be that of a pointer array that contains the addresses of the strings that are to be processed by the five instructions. Referring to the disassembly listing, where we see that the address loaded into A0 is $B22F0, then by observing the data stored at that address, we confirm that such is the case. Figure 11.10 contains a section of the disassembly listing that is relevant to the identification of each address stored in the pointer array, and just enough of the beginning of each string. You could easily confirm that the strings stored at those locations match those of the reassembly listing simply by converting each of the ASCII codes in the disassembly listing to characters. Figure 11.10. The section of the disassembly listing containing the addresses referenced in the pointer array at $B22F0. 0B2302 23D80D0A5445 MOVE.L (A0)+,$A5445 0B2308 5354 SUBQ.W #1,(A4) 0B2328 000D DC.W $D 0B232A 0A544553 EORI.W #$4553,(A4) 0B2362 000D DC.W $D 0B2364 0A544553 EORI.W #$4553,(A4) 0B2392 745F MOVEQ #$5F,D2 0B2394 6D65 BLT.S $B23FB 0B23D6 0A000D0A EORI.B #$A,D0 0B23DA 5445 ADDQ.W #2,D5 We need not be concerned with the actual names used for the labels of the strings; we need only realize that we must place labels at their declarations and store those labels in the pointer array in place of the addresses that are present in the reassembly listing. Let us chose to use "string_zero" for the first, to match the "TEST POINT 0" reference within the string itself, and continue with the rest of them through "string_four". Remember that the pseudo op for the pointer array declaration at L00023 must be dc.l, for two reasons. The first is that 32-bit addresses are being stored in the array; the second is that the run time addresses would not be stored if a ds pseudo op were used. Still within the same subroutine, after the five instructions which lead us to the pointer array, there are a series of loads into A0 followed by branches to the print_line subroutine. The labels referenced in that area are those that we left with the "+1" excess baggage. We can now alter those labels and the references to them to L00024, L00025 and L00026. In addition we can replace the two constant identifiers, K00001 and K0000E by the actual values that are stored in registers D7 and D6. At the conclusion of that activity, we will have arrived at label L00030. At this point, it would be advantageous to exchange each of the constant identifiers remaining in the subroutine for the actual constants. Simultaneously, we can convert upper case statements which require no alterations to lower case as an indication that we need not be concerned about the format of those statements. Figure 11.11 shows the reassembly listing at its current stage of reconstruction. Figure 11.11. The partially reconstructed reassembly listing. K00001=0 K00003=$3C K00004=1 K00006=$46 K00007=$C8 K0000C=$A K0000D=2 K0000E=4 K0000F=6 K00010=8 K00012=$23 K0001A=$17 K0001B=$28 K0001D=5 K00020=$3E K00028=$B K00029=$20 K0002B=$F K0002C=$3A K0002D=3 K00031=9 create_file: lea stack(pc), sp move.w #0, -(sp) pea filename(pc) move.w #$3C, -(sp) trap #1 addq.l #8, sp move.w d0, file_handle redirect_output: move.w file_handle(pc), -(sp) ; CAN USE D0 FOR IMPROVEMENT. move.w #1, -(sp) move.w #$46, -(sp) trap #1 addq.l #6, sp move.w #$C8, d3 lea aes_pb(pc), a5 lea control(pc) lea L0000A(PC), a3 BSR L0000B initialize_application: move.w #$A, (a4) move.w #0, 2(a4) move.w #1, 4(a4) move.w #0, 6(a4) move.w #0, 8(a4) bsr aes BSR L0000B menu_register: move.w #$23, (a4) move.w #1, 2(a4) move.w #1, 4(a4) move.w #1, 6(a4) move.w #0, 8(a4) lea global(pc), a0 move.w 4(a0), int_in move.l #menu_text, addr_in bsr aes move.w int_out(pc), menu_id BSR L0000B move.l #message, addr_in evnt_mesag: move.w #$17, (a4) move.w #0, 2(a4) move.w #1, 4(a4) move.w #1, 6(a4) move.w #0, 8(a4) bsr aes lea message(pc), a0 cmpi.w #$28, (a0) bne.s evnt_mesag move.w 8(a0), d0 cmp.w menu_id(pc), d0 bne.s evnt_mesag cmpi.w #5, L0001E beq.s evnt_mesag BSR L0000B cmpi.w #5, L0001E beq.s close_file bra.s evnt_mesag close_file: move.w file_handle(pc), -(sp) move.w #$3E, -(sp) trap #1 addq.l #4, sp _redirect_output: move.w #1, -(sp) move.w file_handle(pc), -(sp) move.w #$46, -(sp) trap #1 addq.l #6, sp bra.s evnt_mesag L0000B: lea newline(pc), a0 bsr print_line LEA L00023(PC),A0 MOVE.W L0001E(PC),D0 lsl.w #2, d0 ; Multiply by 4. movea.l 0(a0,d0.w), a0 bsr print_line lea L00024(pc), a0 bsr print_line lea L00025(pc), a0 bsr print_line lea L00024(pc), a0 bsr print_line lea L00026(pc), a0 bsr print_line moveq #0, d7 moveq #4, d6 L00030: lea L00027(pc), a0 movea.l a5, a6 move.w #5, d5 move.w #11, d0 L0002A: move.b #$20, (a0)+ ; $20 = ASCII for space. dbra d0, L0002A L0002F: move.w d7, d0 andi.b #$F, d0 move.b 0(a3,d0.w), d0 move.b d0, (a0)+ move.b #$3A, (a0)+ ; $3A = ASCII for colon. move.b #$20, (a0)+ ; $20 = ASCII for space. move.b d7, d0 lsl.w #1, d0 movea.l (a6)+, a1 move.w 0(a1,d0.w), d0 moveq #3, d2 L0002E: rol.w #4, d0 move.b d0, d1 andi.b #$F, d1 ext.w d1 move.b 0(a3,d1.w), d1 move.b d1, (a0)+ dbra d2, L0002E move.b #$20, (a0)+ ; $20 = ASCII for space. move.b #$20, (a0)+ dbra d5, L0002F move.b #0, (a0) lea L00027(pc), a0 bsr print_line lea newline(pc), a0 bsr print_line addi.w #1, d7 dbra d6, L00030 addi.w #1, L0001E rts aes: move.l a5, d1 move.w d3, d0 trap #2 rts print_line: move.l a0, -(sp) move.w #9, -(sp) trap #1 addq.l #6, sp rts data aes_pb: dc.l control,global,int_in,int_out,addr_in,addr_out L00023: dc.l string_zero,string_one,string_two,string_three,string_four string_zero: dc.b $D,$A,'TEST POINT 0: Before appl_init',$D,$A,$D,$A,0 string_one: dc.b $D,$A,'TEST POINT 1: After appl_init, before menu_register',$D,$A,$D,$A,0 string_two: dc.b $D,$A,'TEST POINT 2: After menu_register, before evnt_mesag',$D,$A,$D,$A,0 string_three: dc.b $D,$A,'TEST POINT 3: In message handler, before evnt_mesag',$D,$A,$D,$A,0 string_four: dc.b $D,$A,'TEST POINT 4: In message handler second time',$D,$A,$D,$A,0 L0000A: dc.b '0123456789ABCDEF' newline: dc.b $D,$A,0 dc.b ' AES ARRAYS',$D,$A,0 ; Label is unknown. L00025: dc.b 'CONTROL GLOBAL INT_IN INT_OUT ADDR_IN ADDR_OUT',$D,$A,0 L00026: dc.b '_______ ______ ______ _______ _______ ________',$D,$A,0 L00024: dc.b ' ',$D,$A,0 dc.b ' ',$D,$A,0 ; Label is unknown. menu_text: dc.b ' Accessory Arrays ',0 filename: dc.b 'E:\PRG_8\PRG_8AR.DAT',0 bss align control: ds.w 5 global: ds.w 5 int_in: ds.w 5 int_out: ds.w 5 addr_in: ds.w 5 addr_out: ds.w 5 file_handle: ds.w 1 L0001E:DC.W K00001 message: ds.w 8 menu_id: ds.w 1 L00027: ds.l 160 ds.l 160 stack: ds.l 1 end I would now like to draw your attention to two particular declarations within the listing. I have marked them with the comment Label is unknown. The first declaration is just below the newline label; the second is just above L00015+1. In the original program, the label at the first declaration was "aes_header"; the label at the second was "spaces". There is no reference to these labels in the reassembly listing because they were never referenced in the original program. You can confirm the omission of the first just by looking at the program's output. The header does not appear. I had intended that it should, therefore, its omission is an error. The second declaration should have been removed from the original program because I replaced the function that was to be performed with the "spaces" declaration with in-line code. You can be sure that you will observe similar errors and superfluous statements in other programs that you reconstruct. In fact, you can be sure that you will sometimes see superflous statements that have been deliberately inserted in a program to hinder a reconstruction of the source program. Other ploys include self-modifying code and hardware devices which provide signals for the program. Examples will be investigated later. Concluding the Reconstruction We can choose to continue with the source program reconstruction by returning to the top of the program and resolve any further label references, or we can immerse ourselves in the subroutine which seems to accomplish most of the work in the program. One activity that can be immediately identified is that which follows the evnt_mesag function invocation. The comparisons performed there; comparing #$28 to message[0], and menu_id to message[4]; clearly marks this as the message handler algorithm; therefore, we can designate it as such. Then, let us turn our attention to the program's major subroutine. The third instruction of the subroutine loads the address of the pointer array declared at L00023 into A0; the fourth moves the contents of the variable declared at L0001E into D0; the fifth multiplies the value of that variable by 4; and in the sixth instruction, D0 is used as an index register to load a new address into A0. We already know that the pointer array contains the addresses of the strings declared just below the pointer array declaration. The series of instructions which setup D0 and A0 so that a selection from that group of strings depends on the value stored at L0001E tend to indicate that the value at that location is dynamic. Indeed, if we search the reassembly listing for other references to L0001E, we see that the value stored there is compared to the value 5 in two instructions, and it is incremented as the last instruction in the subroutine. Since the value stored at L0001E is used in an index register that determines the choice from a group of strings which identify themselves as TEST POINTS, we need little imagination to rename the variable test_number or some other name that is indicative of its function, and then to properly perform a bss declaration. Remember to alter all references to L0001E. Figure 11.12 shows the reconstructed, but untested, listing. Figure 11.12. Reconstructed source listing. ; PRG_8AR.ASM ; MAJOR NOTE: ; THIS PROGRAM MAY NOT FUNCTION CORRECTLY IF TURBO ST IS INSTALLED. ; This program has been reconstructed from PRG_8AR.ACC. create_file: lea stack(pc), sp move.w #0, -(sp) pea filename(pc) move.w #$3C, -(sp) trap #1 addq.l #8, sp move.w d0, file_handle redirect_output: move.w file_handle(pc), -(sp) ; CAN USE D0 FOR IMPROVEMENT. move.w #1, -(sp) move.w #$46, -(sp) trap #1 addq.l #6, sp move.w #$C8, d3 lea aes_pb(pc), a5 lea control(pc), a4 lea L0000A(PC), a3 BSR L0000B initialize_application: move.w #$A, (a4) move.w #0, 2(a4) move.w #1, 4(a4) move.w #0, 6(a4) move.w #0, 8(a4) bsr aes BSR L0000B menu_register: move.w #$23, (a4) move.w #1, 2(a4) move.w #1, 4(a4) move.w #1, 6(a4) move.w #0, 8(a4) lea global(pc), a0 move.w 4(a0), int_in move.l #menu_text, addr_in bsr aes move.w int_out(pc), menu_id BSR L0000B move.l #message, addr_in evnt_mesag: move.w #$17, (a4) move.w #0, 2(a4) move.w #1, 4(a4) move.w #1, 6(a4) move.w #0, 8(a4) bsr aes message_handler: lea message(pc), a0 cmpi.w #$28, (a0) bne.s evnt_mesag move.w 8(a0), d0 cmp.w menu_id(pc), d0 bne.s evnt_mesag cmpi.w #5, test_number beq.s evnt_mesag BSR L0000B cmpi.w #5, test_number beq.s close_file bra.s evnt_mesag close_file: move.w file_handle(pc), -(sp) move.w #$3E, -(sp) trap #1 addq.l #4, sp _redirect_output: move.w #1, -(sp) move.w file_handle(pc), -(sp) move.w #$46, -(sp) trap #1 addq.l #6, sp bra.s evnt_mesag L0000B: lea newline(pc), a0 bsr print_line LEA L00023(PC),A0 move.w test_number(pc), d0 lsl.w #2, d0 ; Multiply by 4. movea.l 0(a0,d0.w), a0 bsr print_line lea L00024(pc), a0 bsr print_line lea L00025(pc), a0 bsr print_line lea L00024(pc), a0 bsr print_line lea L00026(pc), a0 bsr print_line moveq #0, d7 moveq #4, d6 L00030: lea L00027(pc), a0 movea.l a5, a6 move.w #5, d5 move.w #11, d0 L0002A: move.b #$20, (a0)+ ; $20 = ASCII for space. dbra d0, L0002A L0002F: move.w d7, d0 andi.b #$F, d0 move.b 0(a3,d0.w), d0 move.b d0, (a0)+ move.b #$3A, (a0)+ ; $3A = ASCII for colon. move.b #$20, (a0)+ ; $20 = ASCII for space. move.b d7, d0 lsl.w #1, d0 movea.l (a6)+, a1 move.w 0(a1,d0.w), d0 moveq #3, d2 L0002E: rol.w #4, d0 move.b d0, d1 andi.b #$F, d1 ext.w d1 move.b 0(a3,d1.w), d1 move.b d1, (a0)+ dbra d2, L0002E move.b #$20, (a0)+ ; $20 = ASCII for space. move.b #$20, (a0)+ dbra d5, L0002F move.b #0, (a0) lea L00027(pc), a0 bsr print_line lea newline(pc), a0 bsr print_line addi.w #1, d7 dbra d6, L00030 addi.w #1, test_number rts aes: move.l a5, d1 move.w d3, d0 trap #2 rts print_line: move.l a0, -(sp) move.w #9, -(sp) trap #1 addq.l #6, sp rts data aes_pb: dc.l control,global,int_in,int_out,addr_in,addr_out L00023: dc.l string_zero,string_one,string_two,string_three,string_four string_zero: dc.b $D,$A,'TEST POINT 0: Before appl_init',$D,$A,$D,$A,0 string_one: dc.b $D,$A,'TEST POINT 1: After appl_init, before menu_register',$D,$A,$D,$A,0 string_two: dc.b $D,$A,'TEST POINT 2: After menu_register, before evnt_mesag',$D,$A,$D,$A,0 string_three: dc.b $D,$A,'TEST POINT 3: In message handler, before evnt_mesag',$D,$A,$D,$A,0 string_four: dc.b $D,$A,'TEST POINT 4: In message handler second time',$D,$A,$D,$A,0 L0000A: dc.b '0123456789ABCDEF' newline: dc.b $D,$A,0 dc.b ' AES ARRAYS',$D,$A,0 L00025: dc.b 'CONTROL GLOBAL INT_IN INT_OUT ADDR_IN ADDR_OUT',$D,$A,0 L00026: dc.b '_______ ______ ______ _______ _______ ________',$D,$A,0 L00024: dc.b ' ',0 dc.b ' ',$D,$A,0 menu_text: dc.b ' Accessory Arrays ',0 filename: dc.b 'E:\PRG_8\PRG_8AR.DAT',0 bss align control: ds.w 5 global: ds.w 5 int_in: ds.w 5 int_out: ds.w 5 addr_in: ds.w 5 addr_out: ds.w 5 file_handle: ds.w 1 test_number: ds.w 1 message: ds.w 8 menu_id: ds.w 1 L00027: ds.l 160 ds.l 160 stack: ds.l 1 end Actually, I have assembled the program and tested it. That's why I know that it will not function correctly if my version of TURBO ST is installed. And there are other problems. That's why I was forced to write a program to assist with the corrections that are necessary to make the reconstructed listing produce object code that is identical to the object code from which we have generated the source.