Format specifiers in C
The format specifier is used during input and output. It is a way to tell the compiler what type of data is in a variable during taking input using scanf() or printing using printf(). Some examples are %c, %d, %f, etc.
The format specifier in printf() and scanf() are mostly the same but there is some difference which we will see.
printf(char *format, arg1, arg2, …)
This function prints the character on standard output and returns the number of character printed the format is a string starting with % and ends with conversion character (like c, i, f, d, etc.).
Between both, there can be elements governing the printing format. Below is its description
- A minus(-) sign tells left alignment.
- A number after % specifies the minimum field width to be printed if the characters are less than the size of width the remaining space is filled with space and if it is greater than it printed as it is without truncation.
- A period( . ) symbol separate field width with the precision.
Precision tells the minimum number of digits in integer, maximum number of characters in string and number of digits after decimal part in floating value.
Lets see these..
Character format specifier : %c
For Signed Integer format specifier : %d, %i
Unsigned Integer Format Specifier: %u:
Output: 4294967286 10
Floating-point format specifier : %f, %e or %E
Unsigned Octal number for integer : %o
Unsigned Hexadecimal for integer: %x, %X
String printing: %s
Address Printing: %p
When our intention is to print the memory address of a variable/pointer ‘%d’ will not work because ‘%d’ will try to format an address into a number and values like 0xbfdd812 is clearly not a number, ie we MUST use %p.
Output: The Memory Address of a: 0x7ffc85861624
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scanf(char *format, arg1, arg2, …)
This function take input using standard input (keyboard) and store it in variable accordingly. It returns the number of items successfully read. Formal parameter arg1, agr2, .. must be a pointer
decimal integer : %d
Integer may be octal or in hexadecimal : %i
Double floating-point number : %lf
String input : %s
Character input : %c
Many other format specifiers are also there
1.%u for an unsigned integer.
2.%lld for long long int.
3.%o octal integer without leading zero
4.%x hexadecimal integer without 0x before the number.