Our First Meeting with

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C
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History of C

• 1950 FORTRAN (Formula Translator)
• 1959 COBOL (Common Business Oriented Language)
• 1971 Pascal
• Between 1970-1980 - Ada

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History of C

• 1967 BCPL
• By Martin Richards
• For writing OS and compilers
• 1970 B
• Used to write UNIX OS for DEC PDP-7
• 1972 C
• By Dennis Ritchie
• Used to write UNIX OS for DEC PDP-11
• Now almost all OS are written in C/C

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History of C

• C became popular after a book written by Ritchie
  and Kernighan
• The C Programming Language
• Many variations came up for different platforms
• ANSI (American National Standards Institute)
  approved a standard in 1989

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Programming Tools

• Compiler
• Standard Library
• IDE
• Help files documentations

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Compilers

• What does it do?
• Parse the code
• Tokenize
• Match syntax
• Find Errors
• Prepare object code

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Standard Library

• What does it do?
• Provide implementations of some basic and
  important functions
• Usually these functions are very efficient
• Programmers should use library functions to
  improve performance and portability

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IDE - Integrated Development Environment

• Helps to Write
• Use different color to highlight different type
  of code
• Sometimes shows hints
• Helps to Compile
• Set environment variables
• Linking with libraries

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IDE - Integrated Development Environment

• Helps to Debug
• Execute step by step
• Use breaks
• Watch the values of variables
• Helps to Run

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Help Files and Documentation

• Provide details about
• Syntax
• Keywords
• Library functions
• Examples
• Etc.

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C Files

• Source File
• .c
• Contains the code
• A program may use multiple source files
• Object File
• .obj
• Compiled source file

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C Files

• Header File
• .h
• Contains codes of library functions
• We can also write header files
• Library File
• .lib
• Compiled library function

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C Files

• Executable File
• .exe
• Final program
• Backup File
• .bak
• Other Files

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Lifecycle of a C Program
Source File
User defined Header File
Standard Header File
Compile
Compile
Compile
Library File
Object File
Link
Executable File
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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• include
• Must be written first
• Means we want to include or use the functions
  defined in the header

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• include
• symbol indicates a preprocessor
• It means it has to be done before compilation

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• ltstdio.hgt
• Name of the header file
• You must know which header you need
• Use help and documentation to find out

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• ltstdio.hgt
• Enclosed in lt gt (header in default place)
• May be enclosed in (header is in the same
  folder as the source)

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• main
• Every C program must have a main function
• Program starts from the 1st line in main

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• main
• Functions has parameters enclosed in ( )
• Functions may return values

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• The curly braces are like containers
• The code between two braces are called a block

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• Missing either brace will generate compile error
• Compound Statement missing

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• printf
• A function given in stdio.h
• Prints the text given as the parameter

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• (semicolon)
• Every C statement must end with a
• Otherwise compiler will generate an error
• Statement Missing

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A first look at C

• include ltstdio.hgt
• void main(void)
• printf(First C Program)

• Keywords
• The texts in White are keywords
• These are words that has special meanings for C

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Another Example

• / My second C Program/
• include ltstdio.hgt
• void main(void)
• printf(My Second C Program\n)

// main function
\n
//end of code
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Another Example

• / My second C Program/
• Enclosed within / and /
• This is a multi-line Comment
• It is not part of the code
• Compiler ignores it
• Used for helping the programmer to understand the
  code better

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Another Example

• // main function
• This is a single-line Comment

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Another Example

• \n
• This is an escape sequence
• \ is escape character
• It indicates that printf should do something
  different with the character that follows the \

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Another Example

• \n
• \n new line (like an enter key)
• \t tab
• \a alert (the PC speaker gives a beep)
• \\ \ (to print \)
• \ (to print or )

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Yet Another Example

• include ltstdio.hgt
• void main(void)
• int a // declaring a variable
• a 10 // assign a value
• printf(The Value of a is d, a)

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Yet Another Example

• int a
• int is a keyword
• It means that the variable declared here is an
  integer
• So int defines the data type
• C has many data types

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Yet Another Example

• int a
• a is the variable name
• The statement creates/defines a new variable
  named a
• Creating a variable means reserving a memory
  location for it
• The size of the memory needed depends on the data
  type

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Yet Another Example

• a 10
• This is an assignment statement
• This means the value 10 is written in the
  memory location reserved for a
• Before using a variable or assigning a value, we
  have to define it first
• Or a compile error Unknown identifier/
  Undefined Symbol will occur

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Yet Another Example

• printf(The Value of a is d, a)
• This is the way a variables value can be
  outputted
• The first parameter is format control string.
• The format and layout of output text is defined
  here

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Yet Another Example

• printf(The Value of a is d, a)
• d is a conversion specifier
• It tells the printf function that it has to print
  the value of an integer variable here

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Yet Another Example

• printf(The Value of a is d, a)
• The second parameter tells the printf function
  the value that should be printed in place of the
  d

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Todays Last Example

• include ltstdio.hgt
• void main(void)
• int a // declaring a variable
• printf(Please enter value of a)
• scanf(d, a) // inputs a value
• printf(\nThe Value of a is d, a)

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Todays Last Example

• scanf(d, a)
• scanf is another function given in stdio.h
• It is used to take inputs from the user
• Syntax is similar to printf

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Todays Last Example

• scanf(d, a)
• NOTE
• Here the variable name is preceded by symbol.
• It indicates the address of the memory location
  that was reserved for a
• Omitting the symbol will cause wrong results

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Looking Back

• We learned about the history of C
• We learned what tools is needed for software
  development
• We learned the important files associated with C

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Looking Back

• Every C Code begins with the include directive
• Every C Program must contain one and only one
  function named main
• A program should have comments to make it easy to
  understand

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Looking Back

• Variables must be defined before they can be used
• printf is used to output
• scanf for input
• We learned about escape sequence
• We also learned about conversion specifier

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Looking Back

• We learned about a few compile errors
• Statement missing
• Compound Statement missing
• Unknown identifier

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Start Practicing