Character Set of C Programming Language

Character Set

The C character set consists of upper and lowercase alphabets, digits, special characters and white spaces. The alphabets and digits are altogether called as the alphanumeric character.

1. Alphabets

A B C D E F ………..Z

a b c d e f ………….z

2. Digits

0 1 2 3 4 5 6 7 8 9

3. Special Characters

4. White space characters

Blank space newline carriage return

Form feed horizontal tab vertical tab

Escape Sequence: The escape sequence is used in C programming language. The escape sequence helps in managing the programs. These are also known as backslash character constants

Identifiers and Keywords

Every word in C programming language is classified either as identifier or keyword. Identifiers are used to name the variables, symbolic constants, function, etc. Keywords are reserved words and they have predefined meanings and cannot be changed by the user. Identifier names have particular rules, such as:

1. Identifier name must begin with a letter and must be a sequence of letters and digits.
2. The underscore character (‘_’) is considered as the letter.
3. All the keyword must be in small letters. They have reserved works and they cannot be treated as a variable in the program. They use specified syntax.
4. The C language is case sensitive. For example, rate, Rate and RATE are treated as three different types of data.
5. For any internal identifier name, at least 31 characters are significant.

The keywords are:

• Auto double int struct
• Break else long switch
• Case enum registers typedef
• Char extern return union
• Const float short unsigned
• Continue for signed-unsigned
• Default go to size of volatile
• Do if static while

Variables

A variable is an entity that has a value and is known to the program by name. The value of the variable changes during each execution. The variable definition associated with memory location is with the variable name. A variable can have only one value assigned to it in every time of execution of the program. Its value can change in different executions.

Example

F= 1.8 * c +32

The above example tells that f and c are the variables. Their values will be changed while the program executes.

Naming a Variable

Since, a variable has a name, let us give some example of valid variables.

I, rank, max, min, class_mark, stud_name,emp_no, Mark, StudName, etc. are valid variables names.

Here are some invalid variables names.

• Sun’s illegal character (‘)
• Fine doubled blank space not allowed
• 5square first character should be letter
• teacher, sal comma not allowed

The variable described above can be put into two categories, namely, globally variable and local variable. The variables defined before the main () are considered as the global variable and the variables within the function or program modules are local variables.

The global variable can be accessed from any subprogram or module or function whereas the local variables are confined within the same module or function.

Example:

In the above example, int a is the declaration of a variable. The variable “an” is considered as a global variable which has effect throughout the program and it can be used anywhere in the program.

Same Data Types

The C language uses various data types. Some of the most important and common data types are listed below:

• Char a single byte that can hold one character
• Int an integer
• Float a single precision floating point number
• Double a double precision floating point number

Note: Precision refers to the number of significant digits after the decimal point. In another sense, it is the accuracy to a certain decimal number.

Qualifier

A qualifier alters the characteristics of the data types such as size or sign. The qualifier that alters the size is short and long. They are applicable to the integers.

Example of Size Qualifier

• Short int integer represented by a lesser number of bits (usually 16)
• Long int integer represented by a greater number of bits (usually 32)
• The qualifier long can be used along with the double precision floating point type.
• Long double an extended precision floating point number

Examples of Sign Qualifier

The sign qualifiers are signed and unsigned. The sign qualifiers combine the inter-data types (int, short int, and long int) resulting in six more type of data.

• signed chart int
• unsigned short int
• signed int
• unsigned int
• signed long int
• unsigned long int
• The sign qualifier can be used with the character also.
• signed char
• unsigned char

Note: The size qualifier short and long cannot be applied to the data types char and float, and sing qualifies signed and unsigned cannot be applied to float, double and long double.

The following table gives us the idea of the total numbers of bits and number range that can be used in all IBM PC.

Declaration of Variables

The variables are necessarily defined before they are used. For this purpose, we use the following conventions.

data type v1,v2, …… vn;

Here, data type refers to the type of the data and v1,v2, etc.., respectively represent different data in single line.

Example: The following way declaring variables are more appropriate.

The last example, int no=10, represents the assignment of 10 to a variable no which is integer type of data. This is an assignment operation. Similarly, the other assignments are:

int filament =100;

char no = ‘x’;

double balance = 25. 28;

The process of giving the initial value to variables is called initialization. C allows the initialization of more than one variable in one statement using multiple assignment operators.

Example of Multiple Assignments

P = q = r = 0;

a = b =c = min;

Example of Assignments

Float x, p;

double y, q;

unsigned k;

Example of Declarations

int m = 5444;

long int n = 12345678;

Example of Assignments

x = 1.23456;

y = 9.887654;

k = 54321;

P = q = 100;

Example of Printing

printf(“\nm = %d”,m);

printf(“\nmn= ”,n);

printf(“\nx = %f”,x);

printf(“\ny = %2.12f”,y);

printf(“\nk = %u” p = %f q = % 1.21f”, k,p,q);

References:

Khanal, R.C. Khanal, R.C. Computer Concept for XII. Pashupatigriha Marga, Thapathali, Kathmandu, Nepal: Ekta Books Distributors Pvt. Ltd., 2010. 134-139.

Adhikari, Deepak Kumar.,et.al., Computer Science XII,Asia Publication Pvt.Ltd