C Characters Set
- Characters set are used to form of words, numbers and statements.
- Like natural languages, computer language will also have well defined characters set, which is useful to build the programs.
- In C language used the following characters set-
1. Letters (Alphabets)
Uppercase (Capital Letters) A…Z
Lowercase (Small Letters) a…z
2. Digits
All decimal digits: 0,1,2,….9 (10 Digits).
3. Special Characters
C language contains the following special character in association with the letters and digits.
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Special Characters |
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Symbol Meaning |
Symbol Meaning |
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~ Tilde { Left brace } Right brace [ Left bracket ] Right bracket ( Lest parenthesis ) Right parenthesis < Opening angle bracket > Closing angle bracket * Asterisk + Plus sign / Slash – Minus sign % Percent sign & Ampersand | Vertical bar |
! Exclamation mark # Number sign (Hash) $ Dollar sign : Colon ^ Caret “ Quotation mark ; Semicolon ? Question mark _ Underscore , Comma . Period \ Backslash ` Apostrophe = Equal to sign |
4. White Spaces
- These characters are not show on the screen (do not Display any indication)
- White spaces may be used to separate words.
- The compiler ignores white spaces unless they are a part of a string constant.
- White space characters are:
– blank space
– horizontal tab
– vertical tab
– carriage return
– form feed
– new line
– Null characters
5. Trigraph Characters
- Many non English keyboard do not support all the characters (Used only non English Keyboard)
- ANSI C introduces the concept of “trigraph” sequences to provide a way to enter certain characters
- Each trigraph sequence consists of three characters (two question marks followed by another character)
Example:
??= # number sign (hash)
??( [ left bracket
??} ] right bracket
??< { left brace
??> } right brace
??/ \ back slash
C-Tokens
- In a C program, individual words/unit and punctuation marks are called tokens.
- C Tokens are smallest units of a program.
- C tokens are the basic buildings blocks in C language which are constructed together to write a C program.
C tokens are six types. They are:
1. Keywords – Pre-defined/In-Built words/Fixed words/Reserved words in compilers. All keywords used in lowercase (small letters). There are 32 keywords used in C language. E.g. int, char, float, void, return, if, do, for, while.
2. Identifiers – It is user/programmer’s define words. refers to name of variable, array, function, structure and union. E.g. a, b , name, add(), fact(), a[i] etc.
3. Constants – Refer to fixed values these values can’t change during program execution. E.g. – 34, -87, 0 (integer constant), 9.455, .0003, 5.0 (float constant), ‘a’, ‘2’, ‘*’ (chars constant), “140 abc” (string constant)
4. Operators – Symbols that perform arithmetic and logical operation. /, *, %, +, – (arithmetic operators), >, <, >=, <=, !, != (relational operators), &&, ||, ! (logical operators) etc.
5. Strings – Group of one or more characters. Enclosed within double quotes. E,g, “Jaipur” , “123, nkgacademy.com”.
6. Special symbols – Punctuation marks. ; (semi-colon used to termination or end of statement of C statement and : is used to declare label name or label value in C.)
Why we read and what benefits of above characters set
and C-Tokens?
- If we learn C characters set and C-tokens then we can write the C Language
Source Code (C Programs)
- In C Program includes the following:
1. Comments
2. Pre-processor
3. C-Tokens and
4. functions (library and user define both)
Explanation with Example:
Here we given C Language code/program area and circumference of circle, in this program we
determine or identify to different terminology used in program.
/* area and circumference of circle */
#include<stdio.h>
#include<math.h>
#define PI 3.14
int main()
{
float r, c, area;
printf("Enter Radius: ");
scanf("%f", &r);
area = PI*pow(r,2);
c = 2 * PI * r;
printf("Radius of Circle = %f\n",r);
printf("Area of circle = %f\n",area);
printf("Circumference = %f\n",c);
return 0;
}
in the above program-
1. /* area and circumference of circle */ is the comments.
2. #include and #define are called pre-processors.
3. stdio.h (standard input output) and math.h are header files.
4. int, float, return are keywords.
5. r, c and area are called identifiers (variable name).
6. PI is constant (float).
7. =, *, & are operators.
8. main() is user define function (compulsory function).
9. printf(), scanf() and pow() are library functions.
10. "Radius of Circle =" is string (or text message) constant.
11. {} braces, () parenthesis, ; semicolon, " and coma (,) are punctuation symbols.
12. %f is format specifier character used in printf() and scanf() function.
