The C Programming Language: A Structured

Language
C is a Structured programming
• Modularity: Programs are divided into smaller, manageable functions, allowing
for independent development and testing.
• Control Structures: C provides clear control structures like loops (for, while) and
conditionals (if, switch) to manage program flow logically.
• Top-Down Approach: Encourages starting with high-level functions and breaking
them down into detailed implementations, aiding in complexity management.
• Clear Flow of Control: Ensures that program execution is explicit and easy to
follow, simplifying debugging and maintenance.
• Ease of Maintenance: Structured design enhances readability and
maintainability, reducing complexity and errors.
• Function-Based Design: Promotes reusability and logical separation of tasks,
reinforcing the structured approach
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The C Programming Language (History)
• 1. Early Influences: BCPL and B
• 1960s: The origins of C can be traced back to languages developed in the
1960s, specifically BCPL (Basic Combined Programming Language), created
by Martin Richards in 1966.
• It was designed for writing system software and provided low-level access to
memory.
• Ken Thompson and B: In 1969, Ken Thompson developed the B programming
language at Bell Labs while working on the UNIX operating system.
• B was based on BCPL and adapted to be a simpler language that could run on
minicomputers with limited memory.

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The C Programming Language (History)
• 2. Creation of C at Bell Labs
• 1970-1972: The B language had limitations in terms of data types and
functionality.
• To overcome these, Dennis Ritchie at Bell Labs began developing C by
expanding and improving upon B.
• C introduced richer data types, structures, and efficient operations, making it
well-suited for both system programming and general-purpose programming.
• 1972: C was fully implemented on a DEC PDP-11 machine.
• Ritchie and his colleagues used C to rewrite the UNIX kernel, replacing
assembly language with a higher-level language that provided portability and
efficiency.

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The C Programming Language (History)
• 3. Early Adoption and Spread of C
• 1973: After the UNIX kernel was rewritten in C, UNIX and C became closely
linked, leading to the rapid adoption of both.
• Late 1970s: C began to gain popularity outside of Bell Labs, especially in
universities and research institutions.
• 4. Standardization: The ANSI C Standard
• 1983: The American National Standards Institute (ANSI) established a
committee, X3J11, to formalize the C language and create an official standard.
• 1989: ANSI introduced the ANSI C standard (also known as C89 or ANSI C).
• 990: The International Organization for Standardization (ISO) adopted ANSI C
as ISO C (ISO/IEC 9899:1990)
• 5. Further Revisions and C Standard Updates
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History of ANSI C 5
Characteristics of C
• Structured Language: Supports breaking down programs into functions,
improving readability and modularity.
• Low-Level Access: Allows direct access to memory and hardware, making it ideal
for system programming.
• Rich Set of Operators: Includes a wide range of operators for arithmetic, logic,
and bit manipulation.
• Standard Library: Provides a set of library functions for handling input/output,
math operations, and more.
• Portable: C code can run on various systems with minimal adaptation.
• Efficient Memory Management: Offers functions like malloc() and free() for
manual memory control.
• Extensibility: New functions and libraries can be added as needed.

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Importance of C

• Efficiency: C is close to hardware, allowing fine control over memory and

CPU usage, making it highly efficient.
• Portability: Code written in C is easy to transfer across different platforms
with minimal changes.
• Versatility: C can be used for system programming, embedded systems,
application development, and more.
• Foundation for Other Languages: Many modern languages like C++, Java,
and Python are influenced by C.
• Widely Used for Systems Programming: C is used to develop operating
systems, drivers, and other performance-critical software.

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Sample C Program Format

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Sample C Program Format
• The main is a part of every C program.
• C permits different forms of main statement.
• Following forms are allowed-
• main()
• int main()
• void main()
• main(void)
• void main(void)
• int main(void)

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Sample C Program
//Author Hasan, Date: , Example.c

#include <stdio.h>

int main() {
printf(“Welcome to CSE Department\n");

return 0;
}

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Basic Structure of a C Program

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Executing a C program

Executing a program written in C involves

a series of steps.
1. Creating the program;
2. Compiling the programming
3. Linking the Program with functions that
are needed from the C library
4. Executing the Program

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Executing a C program with Multiple Files

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Translator Program
• Translator program is an • The main types of
essential tool in programming translator programs are
and software development that
• Convert code written in one
programming language into Assemblers
another,
• Typically into a lower-level
language that a computer can
understand and execute.
Interpreter Compilers

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Translator Program
• 1. Assemblers
• Definition: Converts assembly language into machine code.
• Function: Translates symbolic instructions to binary.
• Output: Machine code specific to hardware.
• Use Cases: Systems programming and embedded systems.
• 2. Compilers
• Definition: Translates high-level programming languages into machine code or
intermediate code.
• Function: Analyzes, optimizes, and generates an executable file.
• Output: Executable binary file.
• Phases: Lexical analysis, syntax analysis, semantic analysis, optimization, code
generation.
• Use Cases: Application and system software development.

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Translator Program
• 3. Interpreters
• Definition: Translates high-level languages into machine code line-by-line at
runtime.
• Function: Executes commands directly without generating an intermediate file.
• Output: Immediate execution of high-level code.
• Advantages: Easier debugging and interactive programming.
• Disadvantages: Generally slower than compiled programs.
• Use Cases: Scripting languages and rapid development.

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 Software Development Life Cycle (SDLC)

SDLC is a structured process followed by

software developers and teams to plan,
design, develop, test, and deploy
software applications

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