SOFTWARE DEVELOPMENT IN C CM9041

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SOFTWARE DEVELOPMENT IN CCM904-1

• Lecture 1
• Introduction to C

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Module Structure

• 1 Lecture, 1 Tutorial , 1 Practical per week
• Module Handbook contains details
• teaching team
• class contact,
• reading list
• Assessment
• Web site-www.soc.staffs.ac.uk/rgh1
• lecture notes and practical exercises
• Module handbook to download
• Assignment details

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Origins of C

• 1971 Ritchie and Thompson develop Unix written in
  assembly language
• This Unix wasnt portable, a suitable HLL with
  low level facilities was required
• CPL had been developed in the 60s
• CPL was a large language, later pared down -gt
  BCPL
• Thompson further reduced BCPL -gt B
• Ritchie enhanced B -gt C. Unix was rewritten in C
• Unix C became widely available
• Unix is now portable any machine with a C
  compiler can run Unix

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C Standards and Variants

• 1978 Kernighan Ritchie publish The C
  Programming Language (Traditional C)
• 1990 ANSI Standard (ANSI C)
• Anything written in traditional C will run on an
  ANSI C compiler
• Also available Borland C, Microsoft C

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Characteristics of C

• Suitable for systems programming
• Suitable for applications programming
• Cryptic syntax programs can be written quickly
  but can be difficult to read
• Permissive data typing gives flexibility but
  reduces the number of errors detected at
  compilation time

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Developing a C Program

• Fully understand the problem
• Design a solution
• Test
• Implement in a suitable programming language
• Test
• Release
• Maintain

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Overall Structure of a C program

• include ltstdio.hgt
• DEFINITION OF ANY CONSTANTS
• int main(void) / some explanatory comment /
• DECLARATIONS
• STATEMENTS
• return 0

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The Pre-Processor
C
Pure C
C Compiler
Object Code
Pre-processor
Object code is executed when the program runs
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Data Types

• Basic Data Types
• int i,j 4 bytes
• float x,y 4 bytes
• double p,q 8 bytes
• char c 1 byte (ASCII)

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• Sizeof Operator
• int i declare an integer variable called i
• sizeof(int) - Gives 4
• sizeof(i) - Gives 4
• Additional Data Types
• long int 8 bytes (263 1) greater range
• short int 2 bytes less storage
• unsigned int 4 bytes greater range, positive
  numbers

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More about the Structure of a C Program

• The Function main
• In C, all code is packaged in functions
• main is the function that the system calls when
  you run your program
• Every program must have one and only one main
• All functions may return a value

Function 1
Function 2
Main statement Call function1 statement statement
Call function 2 return
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Function Components

• A function definition consists of two
• parts
•  A Specification ( or header or interface)
  Specifies the function name, the return value and
  argument list
• A Body ( or block or implementation) Code to be
  executed when the function is called
• A sequence of statements enclosed in braces

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 Expressions and Statements

• A section of code such as n1n2 is called an
  expression
• A statement is a step in a program
• An expression becomes a statement when it
• is terminated by a semicolon

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Comments

• / An example of a C comment /
• A multiline comment can also be used
• /
• This is a multiline
• comment. Indentation is not compulsory
• but it makes the code more readable
• /

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Consideration of two simple examples of a C
program

• include ltstdio.hgt
• define PI 3.14
• int main(void) / calculates the area and the
  circumference of a circle of radius 3 /
• int radius
• float circum, area
• radius3
• circum2PIradius
• areaPIradiusradius
• printf(circumference f\n, circum)
• printf(area f\n, area)
• return 0

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Output (printf statements)

• The printf statement consists of any text to be
  printed plus a format specifier for each argument
•  
• Format Specifiers d, 6d, f, 6.2f, ld, lf,
  c, s
•  
• Special Character Constants for use in control
  strings
• \n newline
• \t tab
• \\ backslash
• \ single quote

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Input (scanf statements)

• Input
• scanf() function is used
• Format scanf(control string, arguments)
• The arguments must be addresses
• e.g.
• int n
• scanf(d, n)
• The is used to obtain the address of n

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include ltstdio.hgt define PI 3.14 int
main(void) / reads the radius of a circle and
then calculates its area and
circumference/ int radius float
circum,area printf(input radius
) scanf(d, radius) circum2PIradius area
PIradiusradius printf(\n\nresults\n\n) pri
ntf(Circle of radius d,radius) printf(\nCircu
mference f and area f\n, circum,area) return
0