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:

max. decimal digits for types a, A, e, E, f, F
max. significant digits for types g, G
min. characters for types d, i, o, u, x, X (leading zeroes for padding)
max. characters for type s
default = 1 for integer types, 6 for floating point types, except for a, A where it is sufficient to distinguish doubles or display an exact value if that is possible
* precision is given by variable of type int

-width:

min. characters to be output (spaces for padding)
-ve value puts padding on right, else it goes on left
* width given by an int

-flags:

+ sign should always be included
a space a space should be included if sign is positive
# leading zero for octal, leading 0x or 0X for hexadecimal, decimal point for floating point number
0 padding to be leading zeroes rather than spaces

-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

c number of characters specified by width is to be read into an array of chars, (default 1), no "\0" is added, whitespace is recorded
[char set] only characters specified will be input
[^char set] only characters not in char set will be input
[]char set] / [^]char set] include "]" in char set

- 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