1. Pointers & Arrays
1-d arrays & pointers
2-d arrays & pointers

2. Pointers pointer to constant value constant pointer to value
const int * p
p can’t change the value of variable it is pointing to
constant pointer to value
int* const p = &j;
p can’t point to anything else, but j.

3. Characters and Strings
A character in ASCII set is represented by integers from 0 – 255.
char data type is used to represent that ASCII set of characters
char ch;
ch = ‘c’; // this is equivalent to ch = 99 because in ASCII table, ‘c’ character’s value is 99.
%c, scanf(“ %c”) to force scanf skip any white space before char
getchar(), returns an int as read from console
char and ints interchangeable (betwee 0 – 255)

4. Characters and Strings
String Literals
sequence of characters enclosed in double quotes.
C treats them as character arrays
When C compiler encounters string literal, it allocates memory to store characters of the string plus one extra character to mark end of string.
This special character is called the null character.
It is represented as first character in ASCII table, i.e. its value is 0 and it is represented as ‘\0’ as character.
The ‘0’ character representing a zero is not same as null character (i.e. the first ASCII character). The ‘0’ character has ASCII value 48.
So, always remember the difference between null character (i.e. ‘\0’) and character zero (i.e. ‘0’)

5. Strings Storing strings char msg[8] = “message”; char msg[8] = “me”;
use character arrays
size should be alteast one more that the number of characters in the string.
the last character should be null.
char msg[8] = “message”;
msg[] => ‘m’, ‘e’, ‘s’, ‘s’, ‘a’, ‘g’, ‘e’, ‘\0’.
char msg[8] = “me”;
msg[] => ‘m’, ‘e’, ‘\0’
char msg[] = “message”;

6. String char *ptr; ptr = “This is a text”; ptr = “this is new text”;
Compiler allocates required memory.
read-only.
ptr = “this is new text”;
this is fine. the pointer can be used to point to other string literal.
Reading strings
gets(str) reads characters including whitespace from console.
str should be allocated memory by user
so, if str is char str[100], it works, but if str is char *str, it wont’.

7. string.h library functions for string manipulations
strlen()
to find the length of the string. It has to be null terminated.
size_t strlen(const char* str)
strcpy()
to copy characters of one string to other
char * strcpy(char *dest, const char* src);
dest should have enough memory allocated to fit string pointed to by src
strncpy()
strcmp
returns 0 if two string match literally

8. Functions Variables scope Global variables static variables
arrays as arguments
void test (int arr[])
void test (int arr[][10])
treated as pointer – so no copy of actual array is made
pass length as argument for function to know about the array’s size.
functions with variable number of parameters
void test (int num, char *str, ….);
atleast one fixed parameter is must
recursive functions

9. Pointer to functions return_type (*pointer_name) (argument list…)
int (*ptr) (int a);
used in callback functions
array of pointers to functions
void (*ptr[20]) (int a)