A Very Simple Program

This program which will print out the message This is a C program

#include <stdio.h>

main()
{
        printf("This is a C program\n");
}

Though the program is very simple, a few points are worthy of note.

Every C program contains a function called main. This is the start point of the program.

#include <stdio.h> allows the program to interact with the screen, keyboard and filesystem of your computer. You will find it at the beginning of almost every C program.

main() declares the start of the function, while the two curly brackets show the start and finish of the function. Curly brackets in C are used to group statements together as in a function, or in the body of a loop. Such a grouping is known as a compound statement or a block.

printf("This is a C program\n");
prints the words on the screen. The text to be printed is enclosed in double quotes. The \n at the end of the text tells the program to print a newline as part of the output.

Most C programs are in lower case letters. You will usually find upper case letters used in preprocessor definitions (which will be discussed later) or inside quotes as parts of character strings. C is case sensitive, that is, it recognises a lower case letter and it's upper case equivalent as being different.

While useful for teaching, such a simple program has few practical uses. Let us consider something rather more practical. The following program will print a conversion table for weight in pounds (U.S.A. Measurement) to pounds and stones (Imperial Measurement) or Kilograms (International).

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