CSCI 130 Chapter 2

Program Components main() #include Variable Definition Function Prototype Program Statements Function Call Function Definition Comments

main() Required in every program –Under normal circumstances: program starts at first statement in main program ends at last statement in main –Ex: void main() { printf(“Hello World”); }

#include Instructs C compiler to add contents of another file during compilation #include statements at top of file Usually called header files (.h) –Some supplied with compiler Never modified –Some user defined Can be modified

Example of #include Library function –#include –greater than, less than indicate library function User defined function –#include “myfile.h” –quotation marks indicate user-defined function –if not in same directory as main file, need to specify the path

Variable Definition Variable - name assigned to a data storage location Must define a variable before it can be used Definition informs compiler of: –variable name –type of data Ex: –int a; –char a, b, c;

Program Statements These statements do the ‘Real’ work One per line, end with semi-colon Statements perform various functions: –input/output write to screen/file/printer accept from screen/file –call functions –perform calculations –other

The Function Call ‘Calling a function’ –asking compiler to execute a function outside of the main() function Ex: –printf(“Hello World”); –doReset() –c = product(a,b)

Function Definition A function: is a self contained block of code performs a specific task A function may be: –a library function printf() –a user defined function doMultiply()

Example of a function, and a function call Function: int doMultiply(int x, int y) { return(x*y); } Function call:...programming statements… c = doMultiply(3,6); …programming statements...

Comments When in doubt - Comment!!! No effect on program execution Any text can be stored in a comment May take up part of a line, a whole line, more than one line Do not be stingy with Comments!!!

Examples of Comments Comments may use one line, part of a line, or more than one line: –/*A single line*/ –for (int x; x<10; x++) /*start of a loop*/ –/*Comments can span multiple lines –as well*/

Philosophy You never have too many comments Too few comments may: –cost you points in this class –cost you friends on the job –cause grey hairs Use comments when the logic is fresh in your mind Crucial to program maintenance