C Programming COP 3223 lecture 1

1
C ProgrammingCOP 3223lecture 1

• Raja Iqbal

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About Myself

• Graduate Student at the School of EECS
• Areas of Interest are Image Compression, Signal
  Processing, Hardware and ASIC Design and FPGA
  Architectures
• Work Experience
• Graduate Research Assistant, School of EECS
• Intel Corporation( Summer/Fall intern)
• Fedex Services (Summer Intern)

3
Pre-requisites

• It is better to have some programming experience
  but I will assume no programming experience.
• Some logic Design background is always helpful

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Todays Objectives

• To recognise the purpose and structure of the
  course
• To develop a good learning strategy
• To build your first program.
• To declare basic C types
• To develop simple programs to do calculations
• To use printf and scanf

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Course Objectives

• To introduce the C programming language
• To provide awareness of the role which C plays in
  modern practical software development
• To study in detail the application of C in the
  integration and maintenance of practical projects

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Course Objectives

• On completion of this syllabus you should be able
  to
• develop software in C using sound software
  engineering principles
• understand the advantages and limitations of C
• demonstrate understanding of the role which C
  plays in practical software development

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Assessment

• Assignments 40
• Lab Attendance and participation in Class
  discussions 10
• Final Exam 25 ( Open Book)
• Surprise Quizzes 25 (Open Book)

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Class meetings

• Thursday 1730- 2000 COMM 101

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Books

• There are millions of books on C Programming. I
  will name few that I like.
• Robert Lafore,Turbo C Programming for the PC and
  Turbo C, Revised Edition, Howard W Sams
  Company
• Herbert Schildt, C The Complete Reference, second
  edition, McGrawHill
• Kernighan, B W, Ritchie, D M The C Programming
  Language (second edition), Prentice Hall, 1983

10
Advice( Do nots)

• Memorise the code without an understanding of
  underlying principles.
• Get your friends to do the coursework for you.
• Aim just to get a passing grade
• Let the instructor proceed in tutorials when you
  have confusions
• Start the coursework the night before it is due.

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Caution

• The C we will use is standard C.
• Any standard C system will do, e.g. Turbo C,
  Unix.
• Experiment with what files you need to bring
  home, if you plan to work at home.
• Avoid machine-specific features

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Advice

• It is your responsibility to make sure that the
  code you are submitting runs correctly on the
  olympus machines.
• You may use any development environment which you
  are comfortable with.

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Using the environment

• For each program that you write create a project
• A project may have one or more files
• ".c" files contain source
• ".h" files we meet later
• ".txt" files are for documentation
• ".cpp" files For this course we will not use
  them
• For this course we will have only one ".c" file

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The Hello World Program

• Traditional first example program
• include ltstdio.hgt
• void main(void)
• printf(Hello, world\n)

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Output
The following will be the output of the Hello
World program Hello, world -
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The compilation process

• Preprocessing (anything beginning is resolved)
• Compiling - generates the object code for each
  source file
• Linking (binding) - links the separate source
  files and the standard libraries to make an
  executable file.

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Syntax errors

• You have broken the C "rules of grammar"
• The compiler may report several errors for one
  mistake
• Fix the syntax errors one at a time and recompile
• Don't despair!
• Warnings have to be fixed too.

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Link-time errors

• After compilation, there may be link errors
• Inconsistent function names
• No "main"
• More than one "main"
• The compiler being awkward (save and re-invoke
  the studio)

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Run-time (semantic) errors

• The program does not do what you want
• This is nearly always your own error
• Look carefully through the code
• Else use the debugger (we meet this later)

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The compiler is picky

• Picks on any minor error
• Has no common sense
• Programming can be frustrating and yet very
  rewarding

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Variables

• To perform calculations we need space to hold
  data. This means declaring variables.
• All variables must have a valid name
• All variables have a type
• Variables may be initialised

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Variable names

• Variable names are example of identifiers.They
  have the following rules
• Must begin with a letter or _
• Followed by zero or more letters, numerals or _
• No spaces allowed
• Case sensitive
• Not a reserve word e.g. int, if, while
• Have to be meaningful

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Are the following variable names valid?

• 123
• a123
• _fred
• num people
• num_employees
• num-staff

• Are they the same?
• VALUE
• Value
• value
• VaLuE
• _Value_

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Basic types

• Whole number types
• char
• short int or short
• int
• long int or long

• Floating point types
• float
• double
• long double

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Example declarations

• int counter1
• long num_records 0
• double length 3.7, width 2.7
• Separation with commas
• Initialisation is optional
• If uninitialised, the value could be anything

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Global and local variables

• A variable declared outside a function (e.g.
  main) is global.
• A variable declared inside a function is local.
• Global variables are like nuclear power
• Some think they should not be used at all.
• Others think that they may be used with great
  caution.

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Rules of number

• Addition a2
• Subtraction a-2
• Multiplication a2
• Unary plus 3.7 same as 3.7
• Unary minus -33

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The problem with division

• What is 5 divided by 2?
• Answer A 2 and a remainder of 1
• This is called integer division
• Answer B 2.5
• This is called real division
• In C both are represented by /

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Rule for division

• If both whole numbers, we get integer division.
• To get remainder we use
• If either or both are floating point we get real
  division
• 5/2 is 2
• 52 is 1
• 5.0/2 or 5/2.0 or 5.0/2.0 is 2.5

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Output of data

• printf always has a format string with zero or
  more places for variable to be written.
• One extra argument per
• printf("There are d people here.\n",
  num_people)
• Types must match or else you will get garbage.

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formats

• d for integer
• e for float in scientific notation
• f for float in decimals
• g chooses e or f format for you
• c for ASCII character
• le for a double in scientific notation
• .2f for float to 2 places of decimals

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Other symbols

• \ or for literal sign
• \" for literal "
• \n for new line
• \t for tab
• \\ for literal backslash

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Input of numbers

• We use a function scanf - part of a larger family
• We must precede each variable by
• We may scan in any amount of data
• scanf("d f", my_int, my_float)
• We use fflush to clear any unmatched input
• fflush(stdin)

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Assignment

• This is a valid C statement
• x 2
• What does it do?
• To copy or store the results of a calculation
• y x 2
• There can be multiple 's on one line
• a 5 b c 2

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Centigrade to Fahrenheit

• 1. Include stdio.h and declare main
• 2. Declare space for variables
• 3. Input the value in centigrade
• 4. Do the calculation
• 5 Output the answer.

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include ltstdio.hgt void main (void) float
cent, fahr printf("Enter temperature in
Centigrade\n") scanf("f",cent) fahr cent
9/5 32 printf("In Fahrenheit this is .2f
degrees\n",fahr)
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Short cut operators

• Why write a a b
• instead write a b
• Works too for -, , /,
• Why write a a 1 or a1
• instead write a or a
• Works too for a-- or --a
• In an expression a done first a done last

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Precedence

• Order in which arithmetic operations are
  evaluated
• (anything in brackets) highest
• unary ,-
• ,/,
• , -
• , , -, etc. lowest

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Unsigned qualifier

• unsigned means that the ve is doubled but the
  -ve range is sacrificed
• unsigned int population
• Int 32768 to 32767
• Unsigned int 0 - 65535

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Casting

• You can change one type to another thus
• int x
• float y
• x (int) y
• Note that this truncates and does not round

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Pitfalls

• There is no check for overflow or underflow -
  you just get garbage
• 3 ab is (3 a) b
• Uninitialised variables contain garbage
• Assigning a higher type to a lower one gives a
  warning - use a cast
• Input of garbage gives a garbage value, unless
  you initialise

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Making code readable

• Keep one statement per line
• Add comments to answer questions
• Do not comment the obvious
• Add lots of spacing
• Indent code
• Try not to be too clever