Introduction to C Programming

Introduction to C Language

• C is a general-purpose computer language that is structured, high-level, and machine-independent.
• It was originally created for writing Operating System software.
• C was evolved from ALGOL, BCPL, and B by Dennis Ritchie at the Bell Laboratories in 1972.
• The language became more popular after the publication of the book ‘The C Programming Language’ by Brian Kerningham and Dennis Ritchie in 1978.

Fundamentals of C Language

• The basic elements of C language can be classified as:
  • Identifiers
  • Keywords
  • Constants
  • C Character set

Identifiers

• Identifiers are names given to various program elements, such as variables, functions, and arrays.
• Identifiers consist of letters and digits in any order, except that the first character must be a letter.
• Identifiers are case-sensitive, and the maximum length is 32 characters.

Keywords (Reserved words)

• Reserved words are essential parts of a language definition.
• These words have special meaning in C, and therefore, they cannot be used as variable names.
• Examples of reserved words include: auto, double, if, static, break, else, int, struct, etc.

Constants

• A constant is a container that stores a value that cannot be changed during program execution.
• There are two broad categories of constants in C: literal constant and symbolic constant.
• Literal constants can be classified into:
  • Integer constants (decimal, octal, hexadecimal)
  • Character constants (character, string)
  • Floating-point constants

Symbolic Constants in C

• A symbolic constant is a name that substitutes for a sequence of characters.
• Symbolic constants are defined using #define and are usually placed at the beginning of a program.

Character Set

• The C programming language requires a set of characters including:
  • Alphabets A-Z, a-z
  • Digits 0-9
  • Special symbols # & | ? _ ~ ^ { } [ ] ( ) < > , . : ; ‘ $ “ + - / * =

Basic Data Types in C

• Format specifier or conversion specifier is used to indicate the data type to be printed or scanned.
• Examples of format specifiers include:
  • %c for char
  • %d for int
  • %f for float or double
  • %e for float or double (exponential format)

Variables and Their Declarations

• A variable is an identifier that stores a value that can change during program execution.
• A variable name can be chosen by the programmer in a meaningful way that reflects what it represents in the program.
• The naming convention of a variable follows the rules of constructing identifiers.

Operators

• Operators are special symbols that instruct the compiler to perform certain mathematical or logical manipulations.
• Operators are used with operands to build expressions.
• Examples of operators include:
  • Arithmetic operators (+, -, *, /, %)
  • Relational operators (==, !=, <, >, <=, >=)
  • Logical operators (&&, ||, !)

Expressions

• C expressions are based on algebra expressions.
• An expression is a combination of variables, constants, and operators written according to the syntax of C language.
• Expressions in C evaluate to a value that can be assigned to a variable.

Rules for Evaluation of Expression

• Parethesized sub-expressions are evaluated left to right.
• The precedence rule is applied in determining the order of application of operators in evaluating sub-expressions.
• The associability rule is applied when two or more operators of the same precedence level appear in the sub-expression.