Summary of Module One

Comments
/*     */ comment: possibly over multiple lines
// comment: ignore rest of line

Libraries
#include <stdio.h> load the system library called stdio

Main Program

int main(void)
{
    statements;
    ....
    return 0;
}

- main program block
- gets nothing (void) from operating system
- returns an integer (int) to operating system
- in this case a 0 is returned

printf Function
printf("format string",variable list);
- displays formatted data as specified by format string between inverted commas
- % corresponds to a variable in the variable list whose contents are to be displayed at that position
- % indicates a format specifier giving type and other information for corresponding variable

% flags width .precision size type

- type: given by following table

Format Type Specifier Variable Type Displayed As
d or i int decimal (base 10)
o unsigned int octal (base 8)
u unsigned int decimal (base 10)
x or X unsigned int hexadecimal (base 16)
f or F float or double decimal point but no exponent
e or E float or double decimal point and exponent
g or G float or double uses exponent if needed
a or A float or double hexadecimal (base 16) floating point
c int or char character
s array of char's character string
p pointer address in hexadecimal
n integer store number of characters appearing so far

-size: given by following table

Format Size Specifier Size
h short
l long
ll long long
hh (convert char to int code)

-precision:

-width:

-flags:


-special characters:

Special Character
%% percent sign
\n carriage return
\t tab
\0 end of string

getchar Function

getchar();

- gets single char from user
- returns the actual character obtained

scanf Function

scanf("format string",variable list);

- reads a string from the user in a given format
- returns number of variables successfully filled with data matching format string
- use ampersands in front of variable names unless using arrays
- a % in the format string corresponds to a pointer to a variable in the variable list which can store data of the specified type
- % indicates a format specifier

% * width size type

- type: as for printf except

- width: maximum number of characters to be read
- * do not record data input for this variable

Arrays
type name[size];
- set aside size locations in memory, each of type type and set name to be a pointer to the first such location