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.
