NOTES OF C LANGUAGE

                                                        

                                                   C programing  language

       

                DEPARTMENT OF COMPUTER SCIENCE & INFORMATION TECHNOLOGY

                                              

 for Computer Science & Information Technology

                           

I am a  Shubham  Sharma student of the Information Technology Branch, and I prepared some notes related to computer programming, mathematics and, Database management system(DBMS).
This type of notes is beneficial for the semester exam for revision Theory. 
Thanks.                                                                                                                   

                                                                                                                           

s.no	Content list	Page no.
1.	History of  C	4
2.	Variables and constants	5
3.	Data type operators	5-9
4.	Loop controls and array	10
5.	Function	11
6.	Pointer	12
7.	File handling	13

Brief History of C Programming Language

C is a general-purpose programming language which features economy of expression, modern control flow and data structures, and a rich set of operators. C is not a "very high level" language, nor a "big" one, and is not specialized to any particular area of application. But its absence of restrictions and its generality make it more convenient and effective for many tasks than supposedly more powerful languages.

The history of C programming language is quite interesting. C was originally designed for and implemented on the UNIX operating system on the DEC PDP-ll, by Dennis Ritchie. C is the result of a development process that started with an older language called BCPL. BCPL was developed by Martin Richards, and it influenced a language called B, which was invented by Ken Thompson. B led to the development of C in the 1970s.

For many years, the de facto standard for C was the version supplied with the UNIX operating system. In the summer of 1983 a committee was established to create an ANSI (American National Standards Institute) standard that would define the C language. The standardization process took six years (much longer than anyone reasonably expected).

The ANSI C standard was finally adopted in December 1989

Constants and Variables in C language

CONSTANT

As the name suggests the name constants are given to such variables or values in C programming language which cannot be modified once they are defined. They are fixed values in a program. There can be any types of constants like integer, float, octal, hexadecimal, character constants-etc. Every constant has some range. The integers that are too big to fit into an int will be taken as along. Now there are various ranges that differ from unsigned to signed bits. Under the signed bit, the range of an int varies from -128 to +127 and under the unsigned bit, int varies from 0 to 255.

IDENTIFIER 
The Name of the variable of any data type is called an identifier.
e.g.     int x (here x is identifier).
           

Variables in c

In programming, a variable is a container (storage area) to hold data.

To indicate the storage area, each variable should be given a unique name (identifier). Variable names are just the symbolic representation of a memory location

Data types in C Language

Data types specify how we enter data into our programs and what type of data we enter. C language has some predefined set of data types to handle various kinds of data that we can use in our program. These data types have different storage capacities.

C language supports 2 different type of data types:

•        Primary data types:

These are fundamental data types in C namely integer(int), floating-,point(float), character(char) and void.

•        Derived data types:

Derived data types are nothing but primary datatypes but a little twisted or grouped together like an array, structure, union, and pointer. These are discussed in details later.

The Data type determines the type of data a variable will hold. If a variable x is declared as int. it means x can hold only integer values. Every variable which is used in the program must be declared as what data-type it is.

Integer type

Integers are used to store whole numbers.

Size and range of Integer type on a 16-bit machine:

Type	Size(bytes)	Range
int or signed int  (%d)	2	-32,768 to 32767
unsigned int    (%l)	2	0 to 65535
short int or signed short int	1	-128 to 127
unsigned short int	1	0 to 255
long int or signed long int	4	-2,147,483,648 to 2,147,483,647
unsigned long int	4	0 to 4,294,967,295

size of data type like int, float, char,  etc is machine-dependent.
In a 64-bit machine, the size of int is 4  bytes.,

Floating point type

Floating types are used to store real numbers.

Size and range of Integer type on a 16-bit machine

Type	Size(bytes)	Range
Float (%f)	4	3.4E-38 to 3.4E+38
Double	8	1.7E-308 to 1.7E+308
long double	10	3.4E-4932 to 1.1E+4932

Character type

Character types are used to store characters value.

Size and range of Integer type on a16-bit machine

Type	Size(bytes)	Range
char or signed char(%c)	1	-128 to 127
unsigned char	1	0 to 255

void type

void type means no value. This is usually used to specify the type of functions that return nothing. We will get acquainted with this datatype as we start learning more advanced topics in C language, like functions, pointers, etc.

C Programming Operators

C Arithmetic Operators

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

C 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.

C Assignment Operators

 The assignment operator is used for assigning a value to a variable. The most common assignment operator is =

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.

C Logical Operators

The  expression containing 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.

Operator	Meaning	Example
&&	Logical AND. True only if all operands are true	If c = 5 and d = 2 then, expression ((c==5) && (d>5)) equals to 0.
||	Logical OR. True only if either one operand is true	If c = 5 and d = 2 then, expression ((c==5) || (d>5)) equals to 1.
!	Logical NOT. True only if the operand is 0

C Bitwise Operators

During computation, mathematical operations like addition, subtraction, multiplication, division, etc are converted to bit-level which makes processing faster and saves power.

Bitwise operators are used in C programming to perform bit-level operations.

Operators	Meaning of operators
&	Bitwise AND
|	Bitwise OR
^	Bitwise exclusive OR
~	Bitwise complement
<<	Shift left
>>	Shift right

TYPES OF LOOP CONTROL STATEMENTS IN C:

There are 3 types of loop control statements in C language. They are,

       •        for•        while•        do-while

Syntax for each C loop control statement is given in the below table with description.

Name	Syntax
For	for (exp1; exp2; expr3) { statements; }Where, exp1 – variable initialization ( Example: i=0, j=2, k=3 ) exp2 – condition checking ( Example: i>5, j<3, k=3 ) exp3 – increment/decrement ( Example: ++i, j–, ++k )
While	while (condition) { statements; }where, condition might be a>5, i<10
do while	do { statements; } while (condition);where, condition might be a>5, i<10

ARRAY-

Arrays a kind of data structure that can store a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

Instead of declaring individual variables, such as number0, number1, ..., and number99, you declare one array variable such as numbers and use numbers[0], numbers[1], and ..., numbers[99] to represent individual variables. A specific element in an array is accessed by an index.

All arrays consist of contiguous memory locations. The lowest address corresponds to the first element and the highest address to the last element.

C - Functions

A function is a group of statements that together perform a task. Every C program has at least one function, which is main(), and all the most trivial programs can define additional functions.

You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically the division is such that each function performs a specific task.

A function declaration tells the compiler about a function's name, return type, and parameters. A function definition provides the actual body of the function.

The C standard library provides numerous built-in functions that your program can call. For example, strcat

What are the  Pointers?

A pointer is a variable whose value is the address of another variable, i.e., direct address of the memory location. Like any variable or constant, you must declare a pointer before using it to store any variable address. The general form of a pointer variable declaration is −

type *var-name;

Here, type is the pointer's base type; it must be a valid C data type and var-name is the name of the pointer variable. The asterisk * used to declare a pointer is the same asterisk used for multiplication. However, in this statement the asterisk is being used to designate a variable as a pointer. Take a look at some of the valid pointer declarations −

int    *ip;    /* pointer to an integer */

double *dp;    /* pointer to a double */

float  *fp;    /* pointer to a float */

char   *ch     /* pointer to a character */

The actual data type of the value of all pointers, whether integer, float, character, or otherwise, is the same, a long hexadecimal number that represents a memory address. The only difference between pointers of different data types is the data type of the variable or constant that the pointer points to.

() to concatenate two strings, memcpy() to copy one memory location to another location, and many more functions.

A unction can also be referred to a method or a sub-routine or a procedure, etc.

Basics of File Handling in C

So far the operations using C program are done on a prompt / terminal which is not stored anywhere. But in the software industry, most of the programs are written to store the information fetched from the program. One such way is to store the fetched information in a file. Different operations that can be performed on a file are:

•        Creation of a new file (fopen with attributes as “a” or “a+” or “w” or “w++”)

•        Opening an existing file (fopen)

•        Reading from file (fscanf or fgetc)

•        Writing to a file (fprintf or fputs)

•        Moving to a specific location in a file (fseek, rewind)

•        Closing a file (fclose)

•   FILE *filePointer;

•   So, the file can be opened as

•   filePointer = fopen(“fileName.txt”, “w”)

opening a file

FILE * filePointer;

filePointer = fopen(“fileName.txt”, “r”);

fscanf(filePointer, "%s %s %s %d", str1, str2, str3, &year);

writing a file

FILE *filePointer ;

filePointer = fopen(“fileName.txt”, “w”);

fprintf(filePointer, "%s %s %s %d", "We", "are", "in", 2012);


STRING
collection of characters is called a string.
There are flowing types of functions related to a string.
1.  strlen()
     This function is used to calculate the number of characters used in the string.
   
2.  strlwr()
      This function is used to convert the capital letter into a small letter.
3.  strupr()
      This function is used to convert the small letter into a capital letter.
4.  strncat()
      This function is used to the addition of two string.
5.  strcpy()
      This function is used to copy of one string into another string.
      e.g.  strncpy(B,A)
            Here B string copy the string A i.e sting A will be given.
      
6.  strcmp()
      This function is used to compare the two strings. If both string the same then it gives zero(0) value, otherwise, it gives the difference between of the ASCII value.
       Different meanings of the  two same small letter string and              capital letter string.
        e.g. RAM and ram have a difference.
7.  strcmpi()
      This function is used to compare the two strings. If both string            same then it gives zero(0) value, otherwise, it gives the difference between of ASCII value.
      No  Different meanings of the two same small letter string and capital letter string.
        e.g. RAM and ram have the same meaning.
      
8.  strrev() 
       This function is used to reverse the character.