![What is C??
C is a programming language developed at AT & T’s Bell Laboratories of USA in 1972.
It was designed and written by a man named Dennis Ritchie.
C seems so popular is because it is reliable, simple and easy to use.
Getting Started with C:
Communicating with a computer involves speaking the language the
computer understands, which immediately rules out English as the language of communication
with computer. However, there isa close analogy between learning English language and
learning C language.
Alphabets A, B, ….., Y, Z a, b, ……, y, z
Digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Special symbols ~ ‘ ! @ # % ^ & * ( ) _ - + = | { } [ ] : ; " ' < > , . ? /
Constants, Variables and Keywords:
The alphabets, numbers and special symbols when properly
combined form constants, variables and keywords. Let us see what are ‘constants’ and
‘variables’ in C. A constant is an entity that doesn’t change whereas a variable is an entity that
may change.
Types of C Constants
C constants can be divided into two major categories:
Primary Constants
Integer Constant
Real Constant
Character Constant
onstants
Array
Pointer
Structure
Union
Enum, etc.
Rules for Constructing Integer Constants:
1. An integer constant must have at least one digit.
2. It must not have a decimal point.
3. It can be either positive or negative.
4. If no sign precedes an integer constant it is assumed to be positive.
5. No commas or blanks are allowed within an integer constant.
6. The allowable range for integer constants is -32768 to 32767.](https://image.slidesharecdn.com/cbasicsbyhaseebkhan-171116144401/85/C-basics-by-haseeb-khan-1-320.jpg)
C basics by haseeb khan
- 1. What is C?? C is a programming language developed at AT & T’s Bell Laboratories of USA in 1972. It was designed and written by a man named Dennis Ritchie. C seems so popular is because it is reliable, simple and easy to use. Getting Started with C: Communicating with a computer involves speaking the language the computer understands, which immediately rules out English as the language of communication with computer. However, there isa close analogy between learning English language and learning C language. Alphabets A, B, ….., Y, Z a, b, ……, y, z Digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 Special symbols ~ ‘ ! @ # % ^ & * ( ) _ - + = | { } [ ] : ; " ' < > , . ? / Constants, Variables and Keywords: The alphabets, numbers and special symbols when properly combined form constants, variables and keywords. Let us see what are ‘constants’ and ‘variables’ in C. A constant is an entity that doesn’t change whereas a variable is an entity that may change. Types of C Constants C constants can be divided into two major categories: Primary Constants Integer Constant Real Constant Character Constant onstants Array Pointer Structure Union Enum, etc. Rules for Constructing Integer Constants: 1. An integer constant must have at least one digit. 2. It must not have a decimal point. 3. It can be either positive or negative. 4. If no sign precedes an integer constant it is assumed to be positive. 5. No commas or blanks are allowed within an integer constant. 6. The allowable range for integer constants is -32768 to 32767.
- 2. Rules for Constructing Real Constants: Real constants are often called Floating Point constants. The real constants could be written in two forms—Fractional form andExponential form. Following rules must be observed while constructing real constants expressed in fractional form: 1. A real constant must have at least one digit. 2. It must have a decimal point. 3. It could be either positive or negative. 4. Default sign is positive. 5. No commas or blanks are allowed within a real constant. Rules for Constructing Character Constants: A character constant is a single alphabet, a single digit or a single special symbol enclosed within single inverted commas. Both the inverted commas should point to the left. For example, ’A’ is a valid character constant whereas ‘A’ is not. The maximum length of a character constant can be 1 character. Ex.: 'A' 'I' '5' '=' Types of C Variables An entity that may vary during program execution is called a variable. Variable names are names given to locations in memory. These locations can contain integer, real or character constants. In any language, the types of variables that it can support depend on the types of constants that it can handle. This is because a particular type of variable can hold only the same type of constant. The rules for constructing different types of constants are different. However, for constructing variable names of all types the same set of rules apply. These rules are given below;-
- 3. Rules for Constructing Variable Names 1. A variable name is any combination of 1 to 31 alphabets, digits or underscores. Some compilers allow variable names whose length could be up to 247 characters. Still, it would be safer to stick to the rule of 31 characters. Do not create unnecessarily long variable names as it adds to your typing effort. 2. The first character in the variable name must be an alphabet or underscore. 3. No commas or blanks are allowed within a variable name. 4. No special symbol other than an underscore (as in gross_sal) can be used in a variable name. These rules remain same for all the types of primary and secondary variables. C Keywords Keywords are the words whose meaning has already been explained to the C compiler (or in a broad sense to the computer). The keywords cannot be used as variable names because if we do so we are trying to assign a new meaning to the keyword, which is not allowed by the computer. Some C compilers allow you to construct variable names that exactly resemble the keywords. There are only 32 keywords available in C. 1. auto 2. double 3. int 4. struct 5. break 6. else 7. long 8. switch 9. case 10.enum 11.register 12.typedef 13.char 14.extern 15.return 16.union 17.const 18.float