The printf statement allows you to send output to standard out. For us, standard out is generally the screen (although you can redirect standard out into a text file or another command).
Here is another program that will help you learn more about printf:
Type this program into a file and save it as add.c. Compile it with the line gcc add.c -o add and then run it by typing add (or ./add ). You will see the line “5 + 7 = 12” as output.
Here is an explanation of the different lines in this program:
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The line int a, b, c; declares three integer variables named a, b and c. Integer variables hold whole numbers.
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The next line initializes the variable named a to the value 5.
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The next line sets b to 7.
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The next line adds a and b and “assigns” the result to c. The computer adds the value in a (5) to the value in b (7) to form the result 12, and then places that new value (12) into the variable c. The variable c is assigned the value 12. For this reason, the = in this line is called “the assignment operator.”
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The printf statement then prints the line “5 + 7 = 12.” The %d placeholders in the printf statement act as placeholders for values. There are three %d placeholders, and at the end of the printf line there are the three variable names: a, b and c. C matches up the first %d with a and substitutes 5 there. It matches the second %d with b and substitutes 7. It matches the third %d with c and substitutes 12. Then it prints the completed line to the screen: 5 + 7 = 12. The +, the = and the spacing are a part of the format line and get embedded automatically between the %d operators as specified by the programmer.
