1BEIT105
Module 1
Overview of C
A Brief History of C.
➢ C was invented and first implemented by Dennis Ritchie on a DEC PDP-11 that used the Unix
operating system.
➢ C is the result of a development process that started with an older language called BCPL.
➢ Martin Richards developed BCPL(“Basic Combined Programming Language”), which
influenced a language called B, invented by Ken Thompson.
➢ B led to the development of C in the 1970s.
➢ For many years, the de facto standard for C was the version supplied with the Unix operating
system.
➢ It was first described in The C Programming Language by Brian Kernighan and Dennis Ritchie
➢ In 1983, a committee was established to create an ANSI (American National Standards Institute)
standard that would define the C language.
➢ The standardisation process took six years (much longer than expected).
➢ The ANSI C standard was finally adopted in December 1989, with the first copies becoming
available in early 1990.
➢ The standard was also adopted by ISO (International Standards Organisation), and the resulting
standard was typically referred to as ANSI/ISO Standard C.
➢ In 1995, Amendment 1 to the C standard was adopted, which added several new library functions.
➢ The 1989 standard for C, along with Amendment 1, became a base document for Standard C++,
defining the C subset of C++.
➢ The version of C defined by the 1989 standard is commonly referred to as C89.
➢ work on C continued quietly, leading to a new standard — the 1999 standard for C, usually
referred to as C99. C99 retained nearly all of the features of C89.
➢ The C99 standardization committee focused on two main areas:
o Addition of several numeric libraries.
o Development of innovative new features such as variable-length arrays and the restrict
pointer qualifier.
BIT, Bengaluru-04 1
, 1BEIT105
C Is a Middle-Level Language
➢ C is called a middle-level language.
This doesn’t mean that C is weaker or harder to use than other high-level languages like
ASIC or Pascal. It also doesn’t mean C is as difficult as low-level languages like assembly
language.
➢ C is called a middle-level language because it combines the features of high-level languages
and the control of assembly language. It gives both ease of programming and hardware-
level control.
➢ C as a middle-level language, allows the programmers to work directly with bits, bytes, and
memory addresses.
➢ C code is also very portable. Portability means that it is easy to adapt software written for
one type of computer or operating system to another type.
➢ All high-level programming languages support the concept of data types. A data type
defines a set of values that a variable can store along with a set of operations that can be
performed on that variable.
➢ Common data types: int (integer), char (character), and float (decimal numbers). C also
allows automatic type conversions.
➢ Although C has several built in data types, it is not a strongly typed language, as are
Pascal and Ada.
➢ C is special in that it allows the direct manipulation of bits, bytes, words, and pointers. This
makes it well suited for system-level programming.
BIT, Bengaluru-04 2
, 1BEIT105
➢ C has only a small number of keywords (reserved words used by the language). C89 has 32
keywords, and C99 adds 5 more (total 37). In comparison, BASIC has over 100 keywords!
fewer keywords make C simpler and more flexible.
C Is a Structured Language
➢ Structured Language: A structured language helps you organize a program into smaller, clear
parts.C is called a structured language, even though it’s not fully block-structured. It is similar
to other structured languages like Pascal, ALGOL, and Modula-2.
➢ C is Not Fully Block-Structured: In block-structured languages, one function can be declared
inside another function. But in C, we cannot create a function inside another function because
of this C is called as structured, but not fully block-structured.
➢ Compartmentalization: C programming language supports compartmentalization means
dividing a program into small sections (modules). Each section performs one specific task.
This makes programs easy to understand, test, and debug. One way to achieve
compartmentalization is by using subroutines that employ local (temporary) variables.
➢ Functions and Local Variables: The main structural unit in C is the function. A function
performs one specific task. Each function can work independently without affecting others.
This makes C programs modular and reusable. We can use functions to divide the program
into smaller parts. Local variables (declared inside a function) are used only in that function.
This prevents side effects (changes that affect other parts of the program). Using too many
global variables (variables known throughout the entire program) can cause errors or confusion
in large programs.
➢ Features of Structured Languages: Structured languages provide different loops: while, do-
while, for. The use of goto is discouraged (it makes code confusing). Structured languages are
modern and easier to maintain. Old languages are usually non-structured and harder to use.
➢ Code Blocks in C: Another way to structure code is by using blocks — a group of
statements inside curly braces { }.
{
printf ("Too low, try again.\n");
scanf("%d", &x);
}
BIT, Bengaluru-04 3
, 1BEIT105
C is a Programmer's Language
➢ Programming Languages for Non-Programmers
o COBOL and BASIC were designed mainly for non-programmers.
o COBOL: Created to make programs readable by people without deep technical
knowledge.
o Focused on readability, not on speed or programming efficiency.
o BASIC: Designed to allow non-programmers to write simple programs and solve small
problems easily.
➢ The Birth and Purpose of C
o C was developed by programmers for programmers.
o It provides:
▪ Few restrictions (gives programmers more control)
▪ Few complaints (easy to use for practical coding)
▪ Block structure (organizing code using braces {})
▪ Stand-alone functions
▪ Compact set of keywords (only around 32)
o C combines the efficiency of assembly language with the structured approach of Pascal
or Modula-2, making it powerful and practical.
BIT, Bengaluru-04 4
Module 1
Overview of C
A Brief History of C.
➢ C was invented and first implemented by Dennis Ritchie on a DEC PDP-11 that used the Unix
operating system.
➢ C is the result of a development process that started with an older language called BCPL.
➢ Martin Richards developed BCPL(“Basic Combined Programming Language”), which
influenced a language called B, invented by Ken Thompson.
➢ B led to the development of C in the 1970s.
➢ For many years, the de facto standard for C was the version supplied with the Unix operating
system.
➢ It was first described in The C Programming Language by Brian Kernighan and Dennis Ritchie
➢ In 1983, a committee was established to create an ANSI (American National Standards Institute)
standard that would define the C language.
➢ The standardisation process took six years (much longer than expected).
➢ The ANSI C standard was finally adopted in December 1989, with the first copies becoming
available in early 1990.
➢ The standard was also adopted by ISO (International Standards Organisation), and the resulting
standard was typically referred to as ANSI/ISO Standard C.
➢ In 1995, Amendment 1 to the C standard was adopted, which added several new library functions.
➢ The 1989 standard for C, along with Amendment 1, became a base document for Standard C++,
defining the C subset of C++.
➢ The version of C defined by the 1989 standard is commonly referred to as C89.
➢ work on C continued quietly, leading to a new standard — the 1999 standard for C, usually
referred to as C99. C99 retained nearly all of the features of C89.
➢ The C99 standardization committee focused on two main areas:
o Addition of several numeric libraries.
o Development of innovative new features such as variable-length arrays and the restrict
pointer qualifier.
BIT, Bengaluru-04 1
, 1BEIT105
C Is a Middle-Level Language
➢ C is called a middle-level language.
This doesn’t mean that C is weaker or harder to use than other high-level languages like
ASIC or Pascal. It also doesn’t mean C is as difficult as low-level languages like assembly
language.
➢ C is called a middle-level language because it combines the features of high-level languages
and the control of assembly language. It gives both ease of programming and hardware-
level control.
➢ C as a middle-level language, allows the programmers to work directly with bits, bytes, and
memory addresses.
➢ C code is also very portable. Portability means that it is easy to adapt software written for
one type of computer or operating system to another type.
➢ All high-level programming languages support the concept of data types. A data type
defines a set of values that a variable can store along with a set of operations that can be
performed on that variable.
➢ Common data types: int (integer), char (character), and float (decimal numbers). C also
allows automatic type conversions.
➢ Although C has several built in data types, it is not a strongly typed language, as are
Pascal and Ada.
➢ C is special in that it allows the direct manipulation of bits, bytes, words, and pointers. This
makes it well suited for system-level programming.
BIT, Bengaluru-04 2
, 1BEIT105
➢ C has only a small number of keywords (reserved words used by the language). C89 has 32
keywords, and C99 adds 5 more (total 37). In comparison, BASIC has over 100 keywords!
fewer keywords make C simpler and more flexible.
C Is a Structured Language
➢ Structured Language: A structured language helps you organize a program into smaller, clear
parts.C is called a structured language, even though it’s not fully block-structured. It is similar
to other structured languages like Pascal, ALGOL, and Modula-2.
➢ C is Not Fully Block-Structured: In block-structured languages, one function can be declared
inside another function. But in C, we cannot create a function inside another function because
of this C is called as structured, but not fully block-structured.
➢ Compartmentalization: C programming language supports compartmentalization means
dividing a program into small sections (modules). Each section performs one specific task.
This makes programs easy to understand, test, and debug. One way to achieve
compartmentalization is by using subroutines that employ local (temporary) variables.
➢ Functions and Local Variables: The main structural unit in C is the function. A function
performs one specific task. Each function can work independently without affecting others.
This makes C programs modular and reusable. We can use functions to divide the program
into smaller parts. Local variables (declared inside a function) are used only in that function.
This prevents side effects (changes that affect other parts of the program). Using too many
global variables (variables known throughout the entire program) can cause errors or confusion
in large programs.
➢ Features of Structured Languages: Structured languages provide different loops: while, do-
while, for. The use of goto is discouraged (it makes code confusing). Structured languages are
modern and easier to maintain. Old languages are usually non-structured and harder to use.
➢ Code Blocks in C: Another way to structure code is by using blocks — a group of
statements inside curly braces { }.
{
printf ("Too low, try again.\n");
scanf("%d", &x);
}
BIT, Bengaluru-04 3
, 1BEIT105
C is a Programmer's Language
➢ Programming Languages for Non-Programmers
o COBOL and BASIC were designed mainly for non-programmers.
o COBOL: Created to make programs readable by people without deep technical
knowledge.
o Focused on readability, not on speed or programming efficiency.
o BASIC: Designed to allow non-programmers to write simple programs and solve small
problems easily.
➢ The Birth and Purpose of C
o C was developed by programmers for programmers.
o It provides:
▪ Few restrictions (gives programmers more control)
▪ Few complaints (easy to use for practical coding)
▪ Block structure (organizing code using braces {})
▪ Stand-alone functions
▪ Compact set of keywords (only around 32)
o C combines the efficiency of assembly language with the structured approach of Pascal
or Modula-2, making it powerful and practical.
BIT, Bengaluru-04 4
