This document provides an overview of key concepts in the C programming language, including: - The benefits and features of C like low-level access, structured programming, and modular programming. - The basic data types in C like char, int, float, and how to define variables of these types. - How C functions are structured with single-level and multiple-level functions, and how to identify errors in function definitions. - The input-output functions in C like getchar(), putchar(), gets(), puts() for character- and string-based I/O. - The conditional and loop constructs available in C for control flow.

1. In this session, you will learn to:
Identify the benefits and features of C language
Use the data types available in C language
Identify the structure of C functions
Use input-output functions
Use constructs
Objectives

2. Identifying the Benefits and Features of C Language
Ken Thompson developed a new language called B.
B language was interpreter-based, hence it was slow.
Dennis Ritchie modified B language and made it a
compiler-based language.
The modified compiler-based B language is named as C.

3. C language:
Possesses powerful low-level features of second generation
languages.
Provides loops and constructs available in third generation
languages.
Is very powerful and flexible.
C as a Second and Third Generation Language
3

4. C language:
Offers all essentials of structured programming.
Has functions that work along with other user-developed
functions and can be used as building blocks for advanced
functions.
Offers only a handful of functions, which form the core of the
language.
Has rest of the functions available in libraries. These functions
are developed using the core functions.
Block Structured Language - An Advantage for Modular
Programming
4

5. Features of the C Language
The features that make C a widely-used language are:
Pointers: Allows reference to a memory location by a name.
Memory Allocation: Allows static as well as dynamic memory
allocation.
Recursion: Is a process in which a functions calls itself.
Bit Manipulation: Allows manipulation of data in its lowest form
of storage.
5

6. Using the Data Types Available in C language
The types of data structures provided by C can be classified
under the following categories:
Fundamental data types
Derived data types
6

7. Fundamental Data Types
Fundamental Data Types:
Are the data types at the lowest level.
Are used for actual data representation in the memory.
Are the base for other data types.
Have machine dependent storage requirement.
Are of the following three types:
char
int
float
7

8. The storage requirement for fundamental data types can be
represented with the help of the following table.
Data Number of bytes on a
32-byte machine
Minimum Maximum
char 1 -128 127
int 4 -2^31 (2^31) - 1
float 4 6 digits of precision 6 digits of precision
double 8 14 digits of precision 14 digits of precision
Fundamental Data Types (Contd.)
8

9. Derived Data Types
Derived Data Types:
Are represented in memory as fundamental data type.
Some derived data types are:
short int
long int
double float
9

10. The storage requirement for derived data types can be
represented with the help of the following table.
Data Number of bytes
on a 32-byte
machine
Minimum Maximum
short int 2 -2^15 (2^15) - 1
long int 4 -2^31 (2^31) - 1
double float 8 12 digits of precision 6 digits of
precision
Derived Data Types (Contd.)
10

11. Defining Data
The syntax for defining data is:
[data type] [variable name],...;
Declaration is done in the beginning of a function.
Definition for various data types is shown in the following
table.
Data definition Data type Memory defined Size (bytes) Value assigned
char a, c; char a
c
1
1
-
-
char a = 'Z'; char a 1 Z
int count; int count 4 -
int a, count =10; int a
count
4
4
-
10
float fnum; float fnum 4 -
float fnum1,
fnum2 = 93.63;
float fnum1
fnum2
4
4
-
93.63
11

12. Practice: 1.1
Write the appropriate definitions for defining the following
variables:
1.num to store integers.
2.chr to store a character and assign the character Z to it.
3.num to store a number and assign the value 8.93 to it.
4.i, j to store integers and assign the value 0 to j.

13. Practice: 1.1 (Contd.)
Solution:
1.int num;
2.char chr=’Z’;
3.float num = 8.93;
4.int i, j=0;
13

14. Defining Strings:
Syntax:
char (variable) [(number of bytes)];
Here number of bytes is one more than the number of
characters to store.
To define a memory location of 10 bytes or to store 9 valid
characters, the string will be defined as follows:
char string [10];
Defining Data (Contd.)
14

15. Practice: 1.2
Write the appropriate definitions for defining the following
strings:
1.addrs to store 30 characters.
2.head to store 14 characters.
15

16. Practice: 1.2 (Contd.)
Solution:
1.char addrs[31];
2.char head[15];
16

17. Identifying the Structure of C Functions
In C language, the functions can be categorized in the
following categories:
Single-level functions
Multiple-level functions
17

18. Single Level Functions
Single Level Functions:
Consider the following single-level function:
main()
{
/*print a message*/
printf("Welcome to C");
}
In the preceding function:
main(): Is the first function to be executed.
(): Are used for passing parameters to a function.
{}: Are used to mark the beginning and end of a function. These
are mandatory in all functions.
/* */: Is used for documenting various parts of a function.
18

19. Semicolon (;): Is used for marking the end of an executable
line.
printf(): Is a C function for printing (displaying) constant or
variable data.
Single Level Functions (Contd.)
19

20. Practice: 1.3
Identify any erroneous or missing component(s) in the
following functions:
1. man()
{
printf("This function seems to be okay")
}
2. man()
{
/*print a line*/
printf("This function is perfect“;
}
20

21. Practice: 1.3 (Contd.)
3. main()
}
printf("This has got to be right");
{
4. main()
{
This is a perfect comment line
printf("Is it okay?");
}
21

22. Solution:
1. man instead of main() and semi-colon missing at the end of
the printf() function.
2. mam instead of main() and ‘)’ missing at the end of the
printf() function.
3. ‘}’ instead of ‘{‘ for marking the beginning of the function and
‘{’ instead of ‘}‘ for marking the end of the function.
4. Comment line should be enclose between /* and */.
Practice: 1.3 (Contd.)
22

23. Multiple Level Functions
The following example shows functions at multiple
levels - one being called by another:
main ()
{
/* print a message */
printf ("Welcome to C.");
disp_msg ();
printf ("for good learning");
}
disp_msg ()
{
/* print another message */
printf ("All the best");
}
23

24. The output of the preceding program is:
Welcome to C. All the best for good learning.
In the preceding program:
main(): Is the first function to be executed.
disp_msg(): Is a programmer-defined function that can be
independently called by any other function.
(): Are used for passing values to functions, depending on
whether the receiving function is expecting any parameter.
Semicolon (;): Is used to terminate executable lines.
Multiple Level Functions (Contd.)

25. Practice: 1.4
Identify any erroneous or missing component(s) in the following
functions:
a. print_msg()
{ main();
printf(“bye”);
}
main()
{ printf(“This is the main function”);}
b. main()
{ /*call another function*/
dis_error();
}
disp_err();
{ printf(“Error in function”);}
25

26. Solution:
a. main() is always the first function to be executed. Further
execution of the program depends on functions invoked from
main(). Here, after executing printf(), the program
terminates as no other function is invoked. The function
print_msg is not invoked, hence it is not executed.
b. The two functions, dis_error() and disp_error, are not
the same because the function names are different.
Practice: 1.4 (Contd.)
26

27. Using the Input-Output Functions
The C environment and the input and output operations are
shown in the following figure.
C Environment
Standard Error Device (stderr)
Standard Input Device (stdin) Standard Output Device (stdout)
27

28. Using the Input-Output Functions (Contd.)
These are assumed to be always linked to the C
environment:
stdin - refers to keyboard
stdin - refers to keyboard
stdout - refers to VDU
stderr - refers to VDU
Input and output takes place as a stream of characters.
Each device is linked to a buffer through which the flow of
characters takes place.
After an input operation from the standard input device, care
must be taken to clear input buffer.

29. Character-Based Input-Output Functions
Character-Based Input-Output Functions are:
getc()
putc()
getchar()
putchar()
The following example uses the getc() and putc() functions:
# include < stdio.h>
/* function to accept and display a character*/
main ()
{char alph;
alph = getc (stdin); /* accept a character */
fflush (stdin); /* clear the stdin buffer*/
putc (alph, stdout); /* display a character*/
}
29

30. The following example uses the getchar() and
putchar() functions:
# include < stdio.h >
/* function to input and display a character using the
function getchar() */
main () {
char c;
c = getchar ();
fflush (stdin); /* clear the buffer */
putchar (c);
}
Character-Based Input-Output Functions (Contd.)
30

31. Practice: 1.5
1. Write a function to input a character and display the
character input twice.
31

32. Practice: 1.5 (Contd.)
Solution:
#include <stdio.h>
void displayTwice(char character)
{
printf("You entered: %c%cn", character, character);
}
int main()
{
char inputCharacter;
printf("Enter a character: ");
scanf("%c", &inputCharacter);
displayTwice(inputCharacter);
return 0;
}
32

33. Practice: 1.6
1. Write a function to accept and store two characters in
different memory locations, and to display them one after
the other using the functions getchar() and
putchar().
33

34. Practice: 1.6 (Contd.)
Solution:
/* function to accept and display two characters*/
#include<stdio.h>
main()
{
char a, b;
a=getchar();
fflush(stdin);
b=getchar();
fflush(stdin);
putchar(a);
putchar(b);
}
34

35. String-Based Input-Output Functions
String-based input-output functions are:
gets()
puts()
The following example uses the gets() and puts() functions:
# include < stdio.h >
/* function to accept and displaying */
main ()
{ char in_str {21}; /* display prompt */
puts ("Enter a String of max 20 characters");
gets (in_str); /* accept string */
fflush (stdin); /* clear the buffer */
puts (in_str); /* display input string */
}
35

36. Using Constructs
There are two types of constructs in C language:
Conditional constructs
Loop constructs
36

37. Conditional Constructs
Conditional Constructs:
Requires relation operators as in other programming language
with a slight change in symbols used for relational operators.
The two types of conditional constructs in C are:
if..else construct
switch…case construct
37

38. The Syntax of the if..else construct is as follows:
if (condition)
{
statement 1 ;
statement 2 ;
:
}
else
{
statement 1 ;
statement 2 ;
:
}
Conditional Constructs (Contd.)
38

39. Practice: 1.7
1. Write a function that accepts one-character grade code, and
depending on what grade is input, display the HRA
percentage according to the following table.
Grade HRA %
A 45%
B 40%
C 30%
D 25%
39

40. Practice: 1.8 (Contd.)
Identify errors, if any, in the following function:
#include<stdio.h>
/*function to check if y or n is input*/
main()
{
char yn;
puts("Enter y or n for yes/no");
yn = getchar();
fflush(stdin);
if(yn=’y’)
puts("You entered y");
else if(yn=‘n')
puts("You entered n");
else
puts("Invalid input");
}
40

41. Syntax of switch…case construct:
switch (variable)
{
case 1 :
statement1 ;
break ;
case 2 :
statement 2 ;
:
:
break;
default :
statement
}
Conditional Constructs (Contd.)
41

42. Loop Constructs
The two types of conditional constructs in C are:
while loop construct.
do..while construct.
The while loop construct has the following syntax:
while (condition in true)
{
statement 1 ; loop
statement 2 ; body
}
Used to iterate a set of instructions (the loop body) as long as
the specified condition is true.
42

43. The do..while loop construct:
The do..while loop is similar to the while loop, except that the
condition is checked after execution of the body.
The do..while loop is executed at least once.
The following figure shows the difference between the while loop
and the do...while loop.
Loop Constructs (Contd.)
while
Evaluate
Condition
Execute
Body of
Loop
True
False
do while
Evaluate
Condition
Execute
Body of
Loop
True
False
43

44. Practice: 1.9
1. Write a function to accept characters from the keyboard until
the character ‘!’ is input, and to display whether the total
number of non-vowel characters entered is more than, less
than, or equal to the total number of vowels entered.
44

45. Practice: 1.9 (Contd.)
Solution:
#include <stdio.h>
#include <ctype.h>
void compareNonVowelsToVowels() {
char ch;
int nonVowelCount = 0;
int vowelCount = 0;
printf("Enter characters (input '!' to stop):n");
while (1) {
scanf(" %c", &ch); // Note the space before %c to consume leading
whitespace
if (ch == '!') {
break;
}
45
if (isalpha(ch)) {
ch = tolower(ch); // Convert character to lowercase for easier
comparison
if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u') {
vowelCount++;
} else {
nonVowelCount++;
}
}
}
printf("Total non-vowel characters entered: %dn", nonVowelCount);
printf("Total vowel characters entered: %dn", vowelCount);
if (nonVowelCount > vowelCount) {
printf("More non-vowel characters than vowels.n");
} else if (nonVowelCount < vowelCount) {
printf("More vowels than non-vowel characters.n");
} else {
printf("Equal number of non-vowel and vowel characters.n");
}
}
int main() {
compareNonVowelsToVowels();
return 0;
}

46. 46
# include <stdio.h>
main ()
{
char ch; int i = 0;
puts ("Enter a character :");
ch = getchar ();
do
{
putchar (ch);
i = i + 1;
} while (i < 40);
}
Program to print accept a character and display it on the screen.

47. 47
#include <stdio.h>
main()
{
char chr;
int i = 0;
printf ("Enter a character : ");
chr = getchar();
fflush (stdin);
while (i < 10)
{
putchar(chr);
i = i + 1;
}
}

48. Summary
In this session, you learned that:
C language was developed by Ken Thompson and Dennis
Ritchie.
C language combines the features of second and third
generation languages.
C language is a block structured language.
C language has various features that make it a widely-used
language. Some of the important features are:
Pointers
Memory Allocation
Recursion
Bit-manipulation

49. Summary (Contd.)
The types of data structures provided by C can be classified
under the following categories:
Fundamental data types: Include the data types, which are used
for actual data representation in the memory.
Derived data types: Are based on fundamental data types.
Fundamental data types:
char, int, and float
Some of the derived data types are:
short int, long int, and double float
Definition of memory for any data, both fundamental and
derived data types, is done in the following format:
[data type] [variable name],...;
49

50. Summary (Contd.)
In C language, the functions can be categorized in the
following categories:
Single-level functions
Multiple-level functions
For standard input-output operations, the C environment uses
stdin, stdout, and stderr as references for accessing the
devices.
There are two types of constructs in C language:
Conditional constructs
Loop constructs
50