1. C Fundamentals & Pointers
Overview of C
Structure Of “C” Programs
Flow of C Program
TOKENS
Keywords

2. History of C
C is developed by Dennis Ritchie at AT&T Bell Laboratories, USA
C is a structured programming language
Developed to overcome the problems of previous language such as BCPL,B, Pascal etc.,
Initially developed to use in UNIX OS
Comments in C provides easy readability
C is a powerful language
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5. Basic Structure Of “C” Programs
#include<stdio.h>
#include<conio.h>
void main() {
-- other statements }
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7. Header files
The files that are specified in the include section is called as header file
These are precompiled files that has some functions defined in them
We can call those functions in our program by supplying parameters
Header file is given an extension .h
C Source file is given an extension .c
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8. Main function This is the entry point of a program
When a file is executed, the start point is the main function
From main function the flow goes as per the programmers choice.
There may or may not be other functions written by user in a program
Main function is compulsory for any c program
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9. Writing the first program
#include<stdio.h>
int main() {
printf(“Hello”);
return 0; }
This program prints Hello on the screen when we execute it
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10. Running a C Program Type a program Save it
Compile the program – This will generate an exe file (executable)
Run the program (Actually the exe created out of compilation will run and not the .c file)
In different compiler we have different option for compiling and running. We give only the concepts.
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11. Comments in C Single line comment Multi line comment // (double slash)
Termination of comment is by pressing enter key
Multi line comment
/*….
…….*/
This can span over to multiple lines
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12. “C” language TOKENS
The smallest individual units in a C program are known as tokens
A token is source-program text that the compiler does not break down into component elements
C has 6 different types of tokens viz.
Keywords [e.g. float, int, while]
Identifiers [e.g. main, amount]
Constants [e.g , 100]
Strings [e.g. “SMIT”, “year”]
Special Symbols [e.g. {, }, [, ] ]
Operators [e.g. +, -, *]
C - programs are written using these tokens and the general syntax.
Keywords
Constants
Operators
Strings
Identifiers
Special Symbols
C tokens

13. Keywords in ANSI “C” switch typedef union unsigned void volatile while
long
register
return
short
signed
sizeof
static
struct
int
double
else
enum
etern
float
for
goto if
auto
break
case
char
const
continue
default do

14. Constants
Constants in C are the fixed values that do not change during the execution of a program.
CONSTANTS
Numeric constants
Character constants
Integer Constants
Real Constants
Single Character
Constants
String Constants

15. Data types in C
Used for declaring variables or functions of different types
Type of a variable determines how much space it occupied in storage
Datatypes is classified into
Basic Types or Primitive data types
int, float, double, char
Enumerated Types
Define and assign certain discrete int value
Type Void – No value
Derived Types or Aggregate data types
Pointer Types
Array types
Structure types
Union types
Function types
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16. Data Types- different attributes
Size
Representation
Minimum range
Maximum range
char, signed char
8 bits
ASCII
-128
127
unsigned char
bool 8 bits
255
short, signed short
16 bits
2's complement
-32768
32767
unsigned short
Binary
65535
int, signed int
unsigned int
long, signed long
32 bits
-2,147,483,648
2,147,483,647
unsigned long
4,294,967,295
float
IEEE 32-bit
e-38
e+38
double
long double

17. Variables Variables are data that will keep on changing Declaration
<<Data type>> <<variable name>>;
int a;
Definition
<<varname>>=<<value>>;
a=10;
Usage
<<varname>>
a=a+1; //increments the value of a by 1
We can also declare and define a variable in single shot like this.
int a=10;
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18. Variable names- Rules Should not be a reserved word like int etc.
Should start with a letter or an underscore(_)
Can contain letters, numbers or underscore
No other special characters are allowed including space
Variable names are case sensitive
A and a are different
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19. Input and Output Input Output scanf(“%d”,&a);
Gets an integer value from the user and stores it under the name “a”
Output
printf(“%d”,a);
Prints the value present in variable a on the screen
Format specifiers
%d is the format specifier. This informs to the compiler that the incoming value is an integer value.
Other data types can be specified as follows:
%c – character
%f – float
%lf – double
%s – character array (string)
Printf and scanf are defined under the header file stdio.h
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20. For loops The syntax of for loop is
for(initialisation;condition checking;increment) {
set of statements }
Eg: Program to print Hello 10 times
for(I=0;I<10;I++)
printf(“Hello”);
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21. While loop The syntax for while loop while(condn) { statements; } Eg:
while(a != 0) Output:
printf(“%d”,a);
a--;
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22. Do While loop The syntax of do while loop do { set of statements
}while(condn);
Eg:
i=10; Output: do
printf(“%d”,i);
i--;
}while(i!=0)
While – Entry controlled loop
Do While – Exit controlled loop
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23. Conditional statements
if (condition) { stmt 1; //Executes if Condition is true } else stmt 2; //Executes if condition is false
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24. Conditional statement
switch(var) { case 1: //if var=1 this case executes stmt; break; case 2: //if var=2 this case executes default: //if var is something else this will execute }
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25. Operators Arithmetic (+,-,*,/,%)
Relational (<,>,<=,>=,==,!=)
Logical (&&,||,!)
Bitwise (&,|)
Assignment (=)
Compound assignment(+=,*=,-=,/=,%=,&=,|=)
Shift (right shift >>, left shift <<)
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26. String functions strlen(str) – To find length of string str
strrev(str) – Reverses the string str as rts
strcat(str1,str2) – Appends str2 to str1 and returns str1
strcpy(st1,st2) – copies the content of st2 to st1
strcmp(s1,s2) – Compares the two string s1 and s2
strcmpi(s1,s2) – Case insensitive comparison of strings
Header file to be included is string.h
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27. Numeric functions pow(n,x) – evaluates n^x ceil(1.3) – Returns 2
floor(1.3) – Returns 1
abs(num) – Returns absolute value
log(x) - Logarithmic value
sin(x)
cos(x)
tan(x)
Header file to be included math.h
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28. Procedures Procedure is a function whose return type is void
Functions will have return types int, char, double, float or even structs and arrays
Return type is the data type of the value that is returned to the calling point after the called function execution completes
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29. Functions and Parameters
Syntax of function
Declaration section
<<Returntype>> funname(parameter list);
Definition section
<<Returntype>> funname(parameter list) {
body of the function }
Function Call
Funname(parameter);
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30. Example function
#include<stdio.h> void fun(int a); //declaration int main() { fun(10); //Call } void fun(int x) //definition printf(“%d”,x);
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31. Actual and Formal parameters
Actual parameters are those that are used during a function call
Formal parameters are those that are used in function definition and function declaration
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32. Pointers / Locator / indicator
Pointer is a variable that stores address of another variable
Pointer Variable
Addresses are integers. Hence pointer stores integer data
Size of pointer = size of int
Pointer that stores address of integer variable is called as integer pointer and is declared as int *ip;
Address
Value
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33. Advantages Usage of Pointer Reduces the Code Improves the Performance
Return multiple values from function
Access any memory location
Usage of Pointer
Dynamic Memory Allocation
malloc(), calloc()
Arrays, Functions and Structures

34. Operators used in Pointers
Address
Dereferencing
& *
(Value of)
(Address of)

35. The value ‘3’ is saved in the memory location ‘x100C’
Int i=3;
Value of ‘i’
Address of ‘i’
‘&i’
‘*i’
variable i 3
(Value of i)
X x x x100c x x1014
Address of i
The value ‘3’ is saved in the memory location ‘x100C’

36. Syntax for pointers
(pointer type declaration)
type *identifier ;
Example
Char *cp ;
Int *ip ;
Double *dp ;

37. Pointer Assignment
Int i = 1 , *ip ; //pointer declaration
ip = &i ; //pointer assignment
*ip = 3 ; //pointer assignment

38. Examples
int a; a=10; //a stores 10 int *ip; ip = &a; //ip stores address of a (say 1000) ip : fetches 1000 *ip : fetches 10 * Is called as dereferencing operator
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39. Pointer Arithmetic Lets take this example program
#include<stdio.h>
Void main() {
Int a [5]={1,2,3,4,5} , b , *pt ;
pt = &a[0];
pt = pt + 4 ;
b=a[0] ;
b+=4 ; }
b = 1
b=1+4
b= 5
a[0]
a[1]
a[2]
a[3]
a[4] pt
X x x x100c x1010
a[0]
a[1]
a[2]
a[3]
a[4] b
X x x x100c x1010

40. Predict the output of this code
Void main() {
int num=10;
Int *pnum=NULL; pnum = &num; *pnum += 20; printf("\nNumber = %d", num); printf("\nPointer Number = %d", *pnum); }

41. Number = 10
Pointer Number = 30

42. Eg., int a[10] = {1,2,3,4,5,6,7,8,9,12} ,*p, *q , i; p = &a[2]; q = &a[5]; i = *q - *p; Printf(“The value of i is %d” i ); i = *p - *q; a[2] = a[5] = 0;

43. The value of i is 3
The value of i is -3
The value of i is 0

44. Work to your Brain int a[10] = { 2,3,4,5,6,7,8,9,1,0 }, *p, *q;
p = &a[2];
q = p + 3;
p = q – 1;
p+ + ;
Printf(“The value of p and q are : %d , %d” *p,*q);

45. The value of p and q are : 7 , 7

46. Work to your Brain int main() { int x[2]={1,2},y[2]={3,4};
int small,big;
small=&x[0];
big=&y[0];
min_max(&small,&big);
printf(“small%d big%d",*small,*big);
return 0; }
min_max(int *a,int *b) {
a++;
b++;
return (*a,*b); }

47. Small 2 big 4