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- Like anybody waking up, it is
- hungry. But the computer hungers
- for more information. It checks to
- see if a bootable disk is in drive
- A:. If not, it looks for a hard
- disk with system files.
- A bootable disk is one that
- contains "system files." These
- three are MSDOS.SYS, IO.SYS and
- COMMAND.COM. You might have seen
- COMMAND.COM on some of your
- floppies, but the other two are
- usually hidden on a bootable disk.
- They are there, but you don't see
- them when you type "dir."
- The computer then reads these
- three files. They tell it all
- about becoming a real computer.
- Once it reads these files, it
- knows how to run programs.
- Just like when you read a
- book, the computer puts this
- information in short-term
- memory. On a computer, this is
- the RAM. These are several I.C.
- chips that can hold hundreds of
- thousands of individual bytes.
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- Next, the computer will look for
- files called AUTOEXEC.BAT and
- CONFIG.SYS on the bootable disk.
- These are special files in which
- the user can write instructions to
- tell the computer to automatically
- load chosen programs. If no AUTO-
- EXEC.BAT file is found, the computer
- asks about the date and time.
- The computer has several timing
- crystals which keep its thinking
- organized. One is also used to keep
- track of the time and date. Many
- computers also have a small
- rechargeable battery and an IC chip
- that keeps track of the time even
- when the main power switch is
- turned off. This small part of the
- computer is always awake.
- The timing crystal emits an
- electronic tick, tick, tick at a
- very high rate of speed. The timing
- chip adds these ticks to the time
- and date. The battery keeps this
- going. Whenever the computer is
- turned on, the battery is recharged.
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