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Assembly Source File | 1994-02-25 | 9.9 KB | 434 lines

;***************************** LOAN.ASM ********************************** PAGE 70,132 comment LOAN Payments ------------- Purpose: -------- LOAN is a sample program to show how floating point math can be performed. It will calculate a 12 month table showing what portions of payments go to principal and interest. Using LOAN ---------- To calculate the loan parameters, type "LOAN"<Enter> and enter the loan amount, principal, and interest. The program will do the rest. Floating Point Overview ----------------------- LOAN operates by first allocating 8 floating variables. Then, three of the variables are set to the payment amount, principal, and interest respectivly. Each of the 8 allocated variables are referenced by a number or token. The first variable is #1, the second #2 etc. This makes it vary easy to add two variables by just saying add #1 to #2. When, the calculations are done, they are extracted by calling "text_out" to convert from floating point format to a printable ascii text string. Compiling --------- The commands needed to build LOAN.EXE using MASM are: masm loan; link loan,loan,,alib.lib; include mac.inc include common.inc ;----------------------------------------------------------------------------- extrn library_setup:far extrn lib_error_handler:far extrn clear_screen:far extrn display_string:far extrn library_terminate:far extrn qget_string:far extrn key_or_mouse:far extrn binary_in:far extrn binary_out:far extrn f_divide:far extrn f_multiply:far extrn f_subtract:far extrn f_addition:far extrn text_in:far extrn text_out:far extrn fmove:far extrn round:far ;------------------------------------------------------------------------------ code segment para public 'CODE' assume cs:code, ds:code ;----------------------------------------------------------------------------- ; color db 1bh pspseg dw 0 lib_info_ptr dw 0 lib_info_seg dw 0 copyright_msg db '----------------- LOAN PAYMENT table ------------- ',0 interest_msg db 'What is the interest rate (xx.xx)% ',0 interest_buf db 8 dup (0) amount_msg db 'What is principle remaining ',0 amount_buf db 20 dup (0) payment_msg db 'What is amount of payments ',0 payment_buf db 12 dup (0) header_msg db 'PAYMENT INT-PAID PRIN-PAID PRIN-REMAINING',0 term_dash_msg db '------- -------- ----------- --------------',0 any_key_msg db 'Press any key to continue',0 int_paid_text db 15 dup (0) prin_paid_text db 15 dup (0) prin_remain_text db 15 dup (0) total_prin_paid db 15 dup (0) total_int_paid db 15 dup (0) display_row db 8 month_count db 0 dw 200 dup (0) ;stack stack_ dw 0 ;----------------------------------------------------------------------------- start: cli mov cs:pspseg,es ;save PSP segment mov ax,cs ;get CODE segment mov ss,ax mov ds,ax mov es,ax mov sp,offset stack_ sti ; next, release memory beyond the end of the program ; The definition for ZSEG marks the ; end of the program's code, data and stack area. ; When linking be sure ZSEG is at the end of the program. mov ax,zseg mov bx,cs:pspseg ; mov es,bx sub bx,ax neg bx ; size of program in paragraphs mov ah,4Ah ; resize memory block int 21h mov ax,cs mov es,ax ; ; check if enough memory free to run program ; mov ax,pspseg ;pass psp segment to setup mov bx,8 ;number of floating point variables call library_setup mov lib_info_ptr,si ;save ptr to library info block mov lib_info_seg,es ; see COMMON.INC or LIBRARY_SETUP cmp ax,128 jae got_enough_mem ;jmp if 128k of memory avail mov al,7 mov ah,fatal_return call lib_error_handler jmp exitx got_enough_mem: ; ; clear the screen and display signon ; mov ah,color ;select color mov al,' ' call clear_screen ; ; display copyright message ; mov si,offset copyright_msg mov ah,color mov dx,0100h ;display row call display_string ; prevent an unintended program crash; trap Ctrl+Break, Ctrl+C and ; Ctrl+Alt+Del key combinations ; call BREAK_KEY_INTERCEPT ; ; --- --- --- --- --- ; load floating point variables as follows: token 0 = interest rate ; 1 = prin ; 2 = payment ; 3 = interest paid ; 4 = prin paid ; 5 = temp (x) ; 6 = total int. paid ; 7 = total prin paid ; get varialbes & zero rest ; int = int/1200 ; int paid = int * prin ; prin paid = payment - int paid ; x = prin - prin paid ; if x is positive ; prin = x ; total int = total int + int paid ; total prin= total prin + prin paid ; ; ; get beginning loan amount (prin) ; mov ax,cs mov ds,ax mov es,ax mov si,offset amount_msg mov dx,0201h ;display location mov ah,color call display_string mov cl,10 ;max length of input string mov dx,0222h ;display location mov di,offset amount_buf call qget_string mov ax,1 ;token # call text_in ;es:di point at text, ax=token ; ; get payment amount ; mov si,offset payment_msg mov dx,0301h ;display location mov ah,color call display_string mov cl,07 ;max length of input string mov dx,0322h ;display location mov di,offset payment_buf call qget_string mov ax,2 ;token # call text_in ;es:di point at text, ax=token ; ; get interest rate ; mov si,offset interest_msg mov dx,0401h ;display location mov ah,color call display_string mov cl,05 ;max length of input string mov dx,0422h ;display location mov di,offset interest_buf call qget_string mov ax,0 ;token # call text_in ;es:di point at text, ax=token ; ; zero all remaining variables ; mov ax,0 mov dx,0 ;set value of zero mov bx,3 ;start with token 3 call binary_in mov bx,4 call binary_in mov bx,5 call binary_in mov bx,6 call binary_in mov bx,7 call binary_in ; ; display header line ; mov si,offset header_msg mov dx,0601h ;display location mov ah,color call display_string ; compute int = int/1200 mov bx,5 mov ax,1200 mov dx,0 call binary_in ;token 5 = 1200 mov ax,0 mov bx,5 mov cx,0 call f_divide ;int/1200 -> int ; compute int paid = int * prin month_loop: mov ax,0 ;interest mov bx,1 ;prin mov cx,3 ;int paid call f_multiply mov ax,3 ;int paid call round ; compute prin paid = payment - int paid mov ax,2 ;payment mov bx,3 ;int paid mov cx,4 ;prin paid call f_subtract mov ax,4 call round ; compute x = prin - prin paid mov ax,1 ;prin mov bx,4 ;prin paid mov cx,5 ;temp (x) prin remain call f_subtract ; if x is positive ; prin = x mov bx,5 call binary_out test dh,80h ;check if negative jz loan_cont ; continue if numbers valid jmp view_wait ; jmp if negative loan_cont: mov ax,5 mov bx,1 call fmove ; compute total int = total int + int paid mov ax,6 ;total int paid mov bx,3 ;int paid mov cx,6 ;total int paid call f_addition ; total prin= total prin + prin paid mov ax,7 ;total prin paid mov bx,4 ;prin paid mov cx,7 call f_addition ; ; convert floating values to text ; mov ax,3 ;int paid mov di,offset int_paid_text mov cx,0208h ;buffer sizes call text_out mov ax,4 ;prin paid mov di,offset prin_paid_text mov cx,0209h ;buffer sizes call text_out mov ax,1 ;prin remaining mov di,offset prin_remain_text mov cx,020bh ;buffer sizes call text_out ; print results for this month mov dh,display_row mov dl,1 mov si,offset payment_buf mov ah,color call display_string mov dh,display_row mov dl,10 mov si,offset int_paid_text mov ah,color call display_string mov dh,display_row mov dl,20 mov si,offset prin_paid_text mov ah,color call display_string mov dh,display_row mov dl,30 mov si,offset prin_remain_text mov ah,color call display_string ; check if 12 months printed, month_count = 12 inc display_row inc month_count cmp month_count,12 je show_totals jmp month_loop ; ; now show totals ; show_totals: mov si,offset term_dash_msg mov dh,display_row mov dl,0 mov ah,color call display_string mov ax,7 ;total prin paid mov di,offset total_prin_paid mov cx,0209h ;buffer sizes call text_out mov ax,6 ;total intrest paid mov di,offset total_int_paid mov cx,020bh ;buffer sizes call text_out mov dh,display_row add dh,1 mov dl,7 mov si,offset total_int_paid mov ah,color call display_string mov dh,display_row add dh,1 mov dl,21 mov si,offset total_prin_paid mov ah,color call display_string ; let user view the screen view_wait: mov si,offset any_key_msg mov dh,display_row add dh,3 mov dl,10 mov ah,color call display_string call key_or_mouse ; ; de-activate the Ctrl+Break trap ; call BREAK_KEY_RESTORE ; normal program exit exitx: mov ax,0 call library_terminate mov ax,4C00h int 21h ;------------------------ code ends ;------------------------------------------------------------------------- ; ; This segment definition is needed so linker will put the LIBSEG here ; before the ZSEG. We want ZSEG to be last so memory allocation will ; work correctly. ; LIBSEG segment byte public 'LIB' LIBSEG ENDS ;------------------------------------------------------------------------- ; zseg must be at the end of the program for memory allocation from ; DOS. ; zseg segment para public 'ZZ' zseg ends end start