C was initially used for system development work, particularly the programs that make-up the operating system. C was adopted as a system development language because it produces code that runs nearly as fast as the code written in assembly language.

Some examples of the use of C might be −

 1. Operating Systems

 2. Language Compilers

 3. Assemblers

 4. Text Editors

 5. Print Spoolers

 6. Network Drivers

 7. Modern Programs

 8. Databases

 9. Language Interpreters

 10. Utilities

C as a mother language

C language is considered as the mother language of all the modern languages because most of the compilers, JVMs, Kernals, etc. are written in C language and most of the languages follow c syntax e.g. C++, Java, etc.

It provides the core concepts like an array, functions, file handling, etc. that are being used in many languages like C++, Java, C#, etc.

C as a system programming language

A system programming language is used to create system software. C language is a system programming language because it can be used to do low-level programming (e.g. driver and kernel). It is generally used to create hardware devices, OS, drivers, kernels, etc. For example, the Linux kernel is written in C.

It can't be used in internet programming like java, .net, PHP, etc.

C as a procedural language

A procedure is known as function, method, routine, subroutine, etc. A procedural language specifies a series of steps or procedures for the program to solve the problem.

A procedural language breaks the program into functions, data structures, etc.

C is a procedural language. In C, variables and function prototypes must be declared before being used.

C as a structured programming language

A structured programming language is a subset of procedural language. Structure means to break a program into parts or blocks so that it may be easy to understand.

In C language, we break the program into parts using functions. It makes the program easier to understand and modify.

C as a mid-level programming language

C is considered as a middle-level language because it supports the feature of both low- level and high-level language. C language program is converted into assembly code, supports pointer arithmetic (low level), but it is machine independent (a feature of high level).

Low-level language is specific to one machine i.e. machine-dependent. It is machine-dependent, fast to run. But it is not easy to understand.

A high-Level language is not specific to one machine i.e. machine-independent. It is easy to understand.

Features of C Language

 1. Simple

 2. Machine Independent or Portable

 3. Mid-level programming language

 4. structured programming language

 5. Rich Library

 6. Memory Management

 7. Fast Speed

 8. Pointers

 9. Recursion

 10. Extensible

At this point, you will have your main.cpp file, which you can modify if you like. For now, it just says "Hello World!", so we can run it as is. Hit F9, which will first compile it and then run it.

You now have a running program! You can simply edit main.cpp and then hit F9 to compile it and run it again.

//We will learn CodeBlock IDE later classes.

A 'C' program basically consists of the following parts -

 1.  Preprocessor Commands

 2. Functions

 3. Variables

 4. Statements & Expressions

 5. Comments

Syntax/Format of the program is:-

Note: comments can be placed anywhere inside the program.

For a sample program, we will use the output statement/function of c – printf()

printf() is used to show formatted output. It is the part of standard input/output (stdio.h) library of c.

Syntax-

Sample Program :

Let us look at a simple code that would print the words "Hello World" −

Let us take a look at the various parts of the above program -

The first line of the program #include <stdio.h> is a preprocessor command, which tells a C compiler to include stdio.h file before going to actual compilation.

The next line int main() is the main function where the program execution begins.

The next line /*...*/ will be ignored by the compiler and it has been put to add additional comments in the program. So such lines are called comments in the program. In C, we can write comments on two types :

    1. Multi Line Comment :

There are 2 ways to compile and run the c program, by menu and by shortcut.

By menu

Now click on the compile menu then compile sub-menu to compile the c program. Then click on the run menu then run sub-menu to run the c program.

By shortcut

Or, press ctrl+f9 keys compile and run the program directly. You will see the following output on the user screen.

You can view the user screen any time by pressing the alt+f5 keys. Now press Esc to return to the turbo c++ console.

Managing Console I/O (conio.h)

clear screen by clrscr() function

If you run the c program many times, it will append the output in the previous output. But, you can call clrscr() function to clear the screen. So it will be better for you to call clrscr() function after the main method. This function is the part of conio.h header file.

Example :

Hold output screen by getch() function

As we run the program, output is displayed for a part of second, so we have to press ctrl+f5 key to view the output.

We can use the function- getch() to hold the console prompt while user does not press any key.

Basically getch() is a character input function that comes from conio.h header file and it wait for input of a single character.

Example 1:

Example 2: show message one after one (show msg when user press any key )

Example 3: show message one after one after clearing console.

Set cursor to specific location on console : gotoxy()

When we Execute the program and show any message on console it will be displayed at top left (0,0) corner of the screen.

We can change the postion of message by using the function – gotoxy()

This function is also the part of <conio.h>

It works on Turbo compiler but not on CodeBlock( there is another method for code block)

Note that we can put 80 characters in x coordinatin (left to right) and upto 25 characters in y-coordination (top to bottom)

Example 1: show following output on console – Ram

Ram

Ram

                Ram Ram

Solution : -

Making Time Delay in between two statements: delay()

We can put delay() function anywhere inside the program where we want to wait for a specific time period.

This function comes from DOS.H.

We have to specify the time amount in a millisecond, ie- 1 second = 1000 milliseconds.

Example – The following example will move your name on the console.

Note that delay() and gotoxy() functions can not be used in codeblocks directly.

For delay() we use the Sleep() function which is the part of window.h header file.

Method of  using gotoxy() in codeblock will be discussed later.

Example – The following example will print 5 names. Each name will be printed after 1-second delay. (in CODE::BLOCKS)

The C program follows many steps in execution. To understand the flow of C program well, let us see a simple program first.

4. The object code is sent to the linker which links it to the library such as header files. Then it is converted into executable code. A simple.exe file is generated.

5. The executable code is sent to loader which loads it into memory and then it is executed. After execution, the output is sent to the console.

Here is the Sequence of Execution of C Program :

Characters are printed on the screen through the keyboard but some characters such as newline, tab. backspace cannot be printed like other normal characters. C supports the combination of backslash (\)and some characters from the C character set to print these characters.

These character combinations are known as escape sequences and are represented by two characters.

The first character is "\" and second character is from the C character set. Some escape sequences are given below-

Note:-

Common ASCII values:

A-Z    :    65-90

a-z    :    97-122

0-9    :    48-57

Some Example of Escape characters :

Example 1:

#include  
#include  
void main() { 
clrscr();
printf("Hello C Language"); 
getch();
printf(“\n This	Text is written in New Line ”); 
printf(“\t this is Horizontal Tab”);
printf(“\n My Name is : \”Manish\” ”); 
getch();
}

Output :

Hello C Language

This Text is written in New Line    this is Horizontal Tab

My Name is : “Manish”

Trigraph Characters There is a possibility that the keyboard doesn't print some characters. C supports the facility of "trigraph sequence" to print these characters. These trigraph sequences have three characters.. First two are '??' and third character is any character from C character set. Some trigraph sequences are as given below-

Digraph Characters

They are made of two character instead of 3. They are introduced in C99 Standard.

They are –

// Example of Digraph :
%: include  
void main() <%
printf("Hello C Language"); 
getch();
%>

Do the assignment 1 , before moving to next topic.

C character Set:

A character denotes any alphabet, digit or special symbol used to represent information. Figure shows the valid alphabets, numbers and special symbols allowed in C.

Alphabets         A … Z a … z

Digits            0, 1, 2, 3, 4, 5, 6, 7, 8, 9

Special symbols   ~ „ ! @ # % ^ & * ( ) _ - + = | \ { } [ ] : ; " ' < > , . ? /

Tokens in C The alphabets, numbers and special symbols when properly combined become a Token. A C program consists of various tokens and a token is a keyword, an identifier, a constant, a string literal, or a symbol. For example, the following C statement consists of five tokens −

printf("Hello, World! \n");

The individual tokens are −

printf (
"Hello, World! \n"
)
;

Tokens can be categorized as –

4. Identifier/Variables

5. Operators

6. Delimiters / Separators

Keywords:

There are certain words that are reserved for doing specific tasks. These words are known as keywords and they have standard, predefined meaning in C. They are always written in lowercase.

There are only 32 keywords available in C which are given below-

Additional Keywords in C99

Delimiters-

Delimiters are used for syntatic meaning in C. these are as given below

Data types are the predefine keywords of C library which are used to declare the memory location(variables/identifiers) inside the program to hold some value/constant during the execution of the program.

For all types of constants we have learned before, C provides one or more data type(based on range/size).

C also provides the facility to modify /change the structure of basic data types to create Derived or user-defined data type.

C Qualifiers

Qualifiers alter the meaning of base data types to yield a new data type.

Size qualifiers

Size qualifiers alter the size of a basic type. There are two size qualifiers, long and short. For example:

Sign qualifiers

Integers and floating-point variables can hold both negative and positive values. However, if a variable needs to hold positive value only, unsigned data types are used.

For example:

unsigned variables cannot hold negative value unsigned int;  // positiveInteger;

There is another qualifier signed which can hold both negative and positive only. However, it is not necessary to define a variable signed since a variable is signed by default.

Constant qualifiers

An identifier can be declared as a constant. To do so the const keyword is used.

const int cost = 20;

The value of cost cannot be changed in the program.

Volatile qualifiers

A variable should be declared volatile whenever its value can be changed by some external sources outside the program.

Keyword volatile is used for creating volatile variables.

Integer Types

The following table provides the details of standard integer types with their storage sizes and value ranges −

To get the exact size of a type or a variable on a particular platform, you can use the sizeof() operator. The expressions sizeof(type) yields the storage size of the object or type in bytes. Given below is an example to get the size of int type on any machine −

#include <stdio.h>

#include <limits.h>       //in case error in sizeof()

int main() {

printf("Storage size for int : %d \n", sizeof(int));

return 0;

}

How to find range of integer data types:

Put the 2 exponet number of bits

Like-

printf(“Range of negative integer -%d”, pow(2,15));

printf(“Range of Positive integer %d”, pow(2,15)-1);

Floating-Point Types

The following table provides the details of standard floating-point types with storage sizes and value ranges and their precision −

The header file float.h defines macros that allow you to use these values and other details about the binary representation of real numbers in your programs. The following example prints the storage space taken by a float type and its range values −

#include  
#include  
int main() {
printf("Storage size for float : %d \n", sizeof(float)); 
printf("Minimum float positive value: %E\n", FLT_MIN ); 
printf("Maximum float positive value: %E\n", FLT_MAX ); 
printf("Precision value: %d\n", FLT_DIG );
return 0;
}

When you compile and execute the above program, it produces the following result on Linux −

Storage size for float : 4

Minimum float positive value: 1.175494E-38

Maximum float positive value: 3.402823E+38 

Precision value: 6

The void Type-

The void type specifies that no value is available. It is used in three kinds of

situations −

Examples :

void main()

or

void main(void)

or

int main(void)

or

int main(<command line arguments>)

Variables :

A variable is nothing but a name given to a storage area that our programs can manipulate. Each variable in C has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

syntax to declare a variable:

<data type> <variable_list>; Like-

int a;

float b,c; char gender;

We can also provide values while declaring the variables as given below:

int a=10,b=20;//declaring 2 variable of integer type float f=20.8;

char c='A';

Rules for defining variables

 # A variable can have alphabets, digits, and underscore.

 # A variable name can start with alphabet and underscore only. It can't start with a digit.

 # No white space is allowed within a variable name.

 # A variable name must not be any reserved word or keyword eg. int, float, etc.

 # The length of the name can be 1 to 31 characters long. C99 permits 63 identical characters in the name. Some compilers allow name to be 247 characters long.

 # Name must be unique in it's scope.

Examples of variables-

Assigning value to variable- (use = ) int a=1030;

printf(“the value of a = %d”,a); int b=5;

printf(“the square of %d = %d”,b ,b*b);

#include<stdio.h>

#include<float.h>

int main() {

int c=20;

int b=30;

int a=b=c;

printf("%d",a);

printf("\n%d",b);

a=b=c=0;

   
printf("\n%d\n%d\n%d",a,b,c);

   
getting input from console-

writing expressions in printf-

Scope and Life Cycle of Variable –

Storage classes –

Types of Variables in C

 There are many types of variables in c:

 1. local variable

 2. global variable

 3. static variable

 4. automatic variable

 5. external variable

According to the scope and storage classes as we discussed above, there are following types of variables in c:

    1. local variable

    2. global variable

    3. static variable

    4. automatic variable

    5. external variable

Some More Secretes of C:

printf() returns the integer value to main function. So we can write it like this also-

printf(“%d”, printf(“Hello”));

output:

Hello 5

An operator is a symbol that tells the compiler to perform specific mathematical or logical functions. C language is rich in built-in operators and provides the following types of operators −

 # Arithmetic Operators

 # Relational Operators

 # Logical Operators

 # Assignment Operator

 # Compound Assignment Operator / Shorthand Operator

 # Increment and Decrement Operators (Unary Operators)

 # Bitwise Operators

 # Conditional Operators

 # Misc Operators

Categories of Operators :

 # Unary Operators (- , ++, --)

# Binary Operators

# Ternary Operators

Arithmetic Operators-

An arithmetic operator performs mathematical operations such as addition, subtraction, and multiplication on numerical values (constants and variables).

Example:

Arithmetic Operators-

C Relational Operators-

A relational operator checks the relationship between two operands. If the relation is true, it returns 1; if the relation is false, it returns value 0.

Relational operators are used in decision making and loops.

C Logical Operators:

An expression containing a logical operator returns either 0 or 1 depending upon whether expression results true or false. Logical operators are commonly used in decision making in C programming.

Example  :

Logical Operators

C Assignment and Compound Assignment Operators-An assignment operator is used for assigning a value to a variable. The most common assignment operator is =

Compound Assignment Operators also assign value/result to the variable but they do not overlap the variable’s value, instead, they update the variable's value after doing a specific operation on It.

Example :

Assignment Operators-

Increment and decrement operators:

++ , --

C programming has two operators increment ++ and decrement

-- to change the value of an operand (constant or variable) by 1.

Increment ++ increases the value by 1 whereas decrement -- decreases the value by 1. These two operators are unary operators, meaning they only operate on a single operand.

Example:

Increment and Decrement Operators

Note : -

Here, the operators ++ and -- are used as prefix. These two operators can also be used as postfix like a++ and a--.

Suppose you use ++ operator as prefix like: ++var. The value of var is incremented by 1 then, it returns the value.

Suppose you use ++ operator as postfix like: var++. The original value of var is returned first then, var is incremented by 1.

What is the output of the following?

Bitwise Operators-

The truth tables for &, |, and ^ is as follows −

Assume A = 60 and B = 13 in binary format, they will be as follows −

A = 0011 1100

B = 0000 1101

------------------------------------------

A&B = 0000 1100

A|B = 0011 1101

A^B = 0011 0001

~A = 1100 0011

Bitwise AND operator &-

The output of bitwise AND is 1 if the corresponding bits of two operands is 1. If either bit of an operand is 0, the result of the corresponding bit is evaluated to 0.

Let us suppose the bitwise AND operation of two integers 12 and 25.

12 = 00001100 (In Binary)

25 = 00011001 (In Binary)

Bit Operation of 12 and 25

Bitwise OR operator |

The output of bitwise OR is 1 if at least one corresponding bit of two operands is 1. In C Programming, bitwise OR operator is denoted by |.

Bitwise XOR (exclusive OR) operator ^

The result of bitwise XOR operator is 1 if the corresponding bits of two operands are opposite. It is denoted by ^.

12 = 00001100 (In Binary)

25 = 00011001 (In Binary)

Example #3: Bitwise XOR

Bitwise complement operator ~

Bitwise compliment operator is an unary operator (works on only one operand). It changes 1 to 0 and 0 to 1. It is denoted by ~.

Bitwise complement of any number N is -(N+1).

Shift Operators in C programming

There are two shift operators in C programming:

 # Right shift operator

 # Left shift operator.

Right Shift Operator

Right shift operator shifts all bits towards right by certain number of specified bits. It is denoted by >>.

Left Shift Operator

Left shift operator shifts all bits towards left by certain number of specified bits. It is denoted by <<.

Example #5:

Shift Operators

Conditional Operator / Ternary Operator :

?:

A conditional operator is a ternary operator, that is, it works on 3 operands.

Conditional Operator Syntax

The conditional operator works as follows:

  1. The first expression conditional Expression is evaluated first. This expression evaluates to 1 if it's true and evaluates to 0 if it's false.

  2. If conditional Expression is true, expression1 is evaluated.

    3. If conditional Expression is false, expression2 is evaluated.

Nesting of ternary operator (condition) ? (- ? - ;) : ( - ? - : - ) ;

Operators Precedence in C

Operator precedence determines the grouping of terms in an expression and decides how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has a higher precedence than the addition operator.

For example, x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has higher precedence than +, so it first gets multiplied with 3*2 and then adds into 7.

Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.

When we say Input, it means to feed some data into a program. An input can be given in the form of a file or from the command line. C programming provides a set of built-in functions to read the given input and feed it to the program as per requirement.

When we say Output, it means to display some data on-screen, printer, or in any file. C programming provides a set of built-in functions to output the data on the computer screen as well as to save it in text or binary files.

The Standard Files

C programming treats all the devices as files. So devices such as the display are addressed in the same way as files and the following three files are automatically opened when a program executes to provide access to the keyboard and screen.

The file pointers are the means to access the file for reading and writing purpose. This section explains how to read values from the screen and how to print the result on the screen.

Unformatted Functions

 # These are the functions which can work with specific type of data only.

 # C has three types of Unformatted I/O functions:

    1. Character I/O : getchar(),putchar(),getch(),putch(),getche()

    2. String I/O : gets() , puts()

    3. File I/O : fgets(),fputs(), getc(), putc(), …..

Note-

File I/O functions will be discussed in File Handling Class.

getchar() , putchar() and putch()

This function reads a character-type data from standard input. It reads one character at a time till the user presses the enter key.

The int getchar(void) function reads the next available character from the screen and returns it as an integer. This function reads only single character at a time. You can use this method in the loop in case you want to read more than one character from the screen.

The int putchar(int c) function puts the passed character on the screen and returns the same character. This function puts only single character at a time. You can use this method in the loop in case you want to display more than one character on the screen.

putch() function works same as putchar()

Check the following example −

When the above code is compiled and executed, it waits for you to input some text. When you enter a text and press enter, then the program proceeds and reads only a single character and displays it as follows −

The getch() and getche()

 # These functions read any alphanumeric character from the standard input  device.

 # The getche() accepts and displays the character and forwards the control to the next line of the program.

 # The getch() accepts but does not display the character and forwards the control to the next line of the program.

The gets() and puts

The char *gets(char *s) function reads a line from stdin into the buffer pointed to by s until either a terminating newline or EOF (End of File).

The int puts(const char *s) function writes the string 's' and 'a' trailing newline to stdout.

Ex-1 //Input String using scanf(“%s”)

Ex-2 //Input String using gets()

What will be the output of follwing program ?

puts

Formatted I/O:

printf () and scanf ()scanf()

C library contains several input functions, and scanf() is the most general of them, because it can read a variety of formats. Of course, input from the keyboard is text because the keys generate text characters: letters, digits, and punctuation. When you want to enter, say, the integer 2004, you type the characters 2 0 0 and 4. If you want to store that as a numerical value rather than as a string, your program has to convert the string character-by-character to a numerical value;  that  is  what scanf() does! It converts string input into various forms: integers, floating-point numbers, characters, and C strings. It is the inverse of printf(), which converts integers, floating-point numbers, characters, and C strings to text that is to be displayed onscreen.

scanf() uses a control string followed by a list of arguments. The control string indicates the destination data types for the input stream of characters. The chief difference is in the argument list. The printf() function uses variable names, constants, and expressions. The scanf() function uses pointers to variables. Fortunately, you don't have to know anything about pointers to use the function. Just remember these simple rules:

 # If you use scanf() to read a value for one of the basic variable types, precede the variable name with an &.

 # If you use scanf() to read a string into a character array, don't use an &.

The scanf() function uses whitespace (newlines, tabs, and spaces) to decide how to divide the input into separate fields. It matches up consecutive conversion specifications to consecutive fields, skipping over the whitespace in between. Note how the input is spread over two lines. You could just as well have used one or five lines, as long as you had at least one newline, space, or tab between each entry. The only exception to this is the %c specification, which reads the very next character, even if that character is whitespace.