Source Programs

Programers create programs by writing commands in a high level language. A high level language program consists of lines of text that have been created with a text editor and are kept in a file on the hard disk. For example, here is a complete program in "C" (Java will be discussed later):

#include <stdio.h>
main()
{
  int sum = 0;
  sum = 2 + 2;
  printf( "%d\n", sum );
}

This program could be saved on the hard disk in a file called addup.c. Like all files, it consists of a sequence of bytes. Since it is a text file, these bytes contain character data. You can edit the file with a text editor and print the file on a printer. It does not contain machine instructions. If the bytes are copied into main memory, they cannot run as a program without some extra work being done.

A source program (or source file) is a text file that contains instructions written in a high level language. It can not be executed (made to run) by a processor without some intermediate steps.

Usually a source program is translated into a machine language program An application program called a translater takes a source file as input and produces an executable program (machine language program) as output. For example, the "C" program addup.c could be translated into an executable program. The executable program might be called addup.exe and can be saved on the hard disk. Now the executable version of the program can be copied into main memory and executed.

The word compile means the same thing as translate. So one can say that a source program is compiled into an executable program.