Overview of C Programming Language

Basic Information About C Programming Language

Computer Component

Hardware

• Hardware is the equipment, or the devices, associated with a computer.

Software

• The instructions that tell the computer what to do are called software or programs.
• Program written by programmers

Hardware and software accomplish four major operations:

• Input
• Processing
• Output
• Storage.

Types of Language

High – level Language

• Language in human readable form are known as high – level language.
• E.g. C, C++, Java etc.

Low – level Language

• Language in the form of 0s and 1s is known as low level language.
• Also known as machine language

Types of Error

Syntax Error

• Refers to an error in the syntax of a sequence of characters or tokens for particular programming language.
• Syntax error will be display at compile time.

Logical Error

• Error occurs because of logic of code is known as logical error.
• It will be display at run time.

Compiler and Interpreter

• It is one kind of program to convert high level language into low level language.
• Interpreter check code line by line if error than display error.
• Compiler check whole code and than display list of errors.

Reserve Keywords

• Some words are reserved for special purpose which are known as reserve keywords.
• Reserve keywords are not used as an name of variable, functions, class etc.
• The keywords must be written in lower case only.

Identifiers

• Identifiers refer to the names of variables, functions and arrays.

Rules for identifiers

• Must consists of only letters, digits, or underscore.
• First character must be an alphabet (or underscore).
• Only first 31 characters are significant.
• Cannot use a reserve keyword.
• Must not contain white space.

Constants

• Constants refer to fixed values that do not change during the execution of program.

Backslash Character Constant

Variables

• Variable is a named location of memory that is used to hold a value.
• Its value can be modified during the program execution.
• We can also say that variable is an identifier that is used to represent a single value.

Data Types

• It is a type of data that can be represent in the value of data element.
• It defines the type of constant which is going to store into the variable.
• Compiler will allocate memory for variable based on data type.

Comments

• Sometime we want to write comment in the program which is not an executable part of our source code.

There are two types of comment

Single line comment ( // )

• E.g. // This is a single line comment

Multi line comment ( /* ------------ */)

• E.g. /* Program name : sum.cpp
  Definition : To calculate the sum */

Declaring Variable

• Before using the variable, you have to define variable to give information to compiler.
• Syntax
  Datatype VariableName;
• E.g.
  int StudentId;
  char Name;
  float Average;
  double SumOfSalary;
• Statements used to declare variable is known as declarative statement.
• When we declare a variable
• Space for a variable is set in memory to hold a value of the specified data type.
• That space is associated with the variable name.
• That space is associated with a unique address.
• E.g. int StudentId;

Variable Initialization

• At the time of variable declaration we can assign default value which is known as variable initialization.
• E.g. int StudentId = 25;

Assigning value to variable

• We can also assign the value to the variable.
• The statement which assign value to the variable is known as assignment statement.

C Program Structure

Preprocessor Directive
Global Declaration
User Defined Functions
int main()
{ Local Declaration
Statements }

Output Function : printf()

• printf( ) is a function defined in stdio.h header file.
• It reads data from the computer’s memory and display it on standard output device.
• printf stands for print formatted.
• On success, the total number of characters written is returned otherwise return negative number.
• Syntax :
  printf(“control string”, VariableList);
• Ex.
  Input Code : printf(“Welcome to home”);
  Output is : Welcome to home
  
• Ex.
  Input Code : int StudentId = 10;
  printf(“%d”, StudentId);
  Output is : 10
  
• You can also combine message and value of variable.
• Ex.
  Input Code : int StudentId = 10;
  printf(“Id of student is %d”, StudentId);
  Output is : Id of student is 10
  
• You can also specify the width of field.
  
  
• Syntax :
  printf(“%field-width FS”, VariableName);
• E.g.
  Input Code : int No = 2563;
  printf(“%3d”, No);
  Output : 256
  

Input Function : scanf()

• It is input formatting function.
• It will read data from standard input and stored in given variable.
• scanf stands for scan formatted.
• Remember that leading white spaces are ignored.
• On success, the function returns the number of items successfully read.
• In the case of an input failure before any data could be successfully read, EOF is returned
• Syntax :
  scanf(“Control String”, &VariableList);
• E.g.
  int No;
  scanf(“%d”, &No);
  char Str;
  scanf(“%c”, &Str);
• You can't use message in scanf function.
• If you want to display message for user understanding than use printf function.
• E.g.
  int No;
  printf("Enter one number:¨);
  scanf("%d", &No);
• Width is used to specified that maximum number of characters to be read.
• But if the whitespace character found before width, that only many characters are going to be stored.
• E.g.
  int No;
  scanf(“%2d”, &No);

Operator

• Unary Operator
• Operator which required one operand is known as unary operator.
• Binary Operator
• Operator which required two operand is known as binary operator.
• Ternary Operator
• Operator which required three operand is known as ternary operator.

Goto Statement

• We can change the normal sequence of execution by transferring control to other part of the program using goto statement.
• Syntax: goto label_name;
• Here the label name should be valid identifier which may appear in anywhere in the program.

Break Statement

• The break statement uses to come out from a loop.
• It can be used to force to end the loop before its natural end.
• Remember that break statement can only used with loop statements and switch statement.

Continue Statement

• The continue statement skip the rest part of the loop and transfer control at the beginning of the loop for next iteration.

Switch Statement

• We can choose statements to execute based on some value.
• This can be achieve using nested if….else statement. But it is very complex.
• C language provide switch statement to avoid this type of complexity.