C Basics

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C Basics

• Prof. Shermane Austin

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Learning Programming Language Basics

• Data Types simple
• Expressions
• Relational and Logical Operators
• Conditional Statements
• Arrays
• Iteration
• Memory Allocation
• I/O
• Functions

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Hello World

• //Simple C program
• include ltiostreamgt //input and output library
• include ltstringgt //string library
• using namespace std // predefined objects
• int main() //first function,
• //function delimiter
• cout ltlt Hello world! ltlt endl //output stream
• return 0 //ends execution and
  returns

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Simple Data Types

• Int 32 bit, optional qualifiers long, short
• Float 32 bit, IEEE floating point
• Double 64 bit, optional qualifer long
• Char 8 bit
• Byte 8 bit

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Operators

• Arithmetic
• , -, /,
• - modulus or remainder, integer only, e.g. 234
• Relational
• lt, gt, lt, gt, !,
• (c a) \\ common error is omitting one of the
• Be careful using ! or with floating point
  values, rounding occurs at the machine level
• Logical
• And , e.g. (c lt a) (c gt b)
• Or , e.g. (c lt a) (c gt b)

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Operator shortcuts Compound Assignment

• Increment, Decrement
• , --
• a a 1 \\can be written as a
• a, a, a--, --a
• Position of operator is important, e.g.
• b f(a) \\a is incremented after f(a) call
• c f(a) \\a is incremented before f(a) call
• Compound Assignment Operators
• int a
• a a 5
• a 5
• Can be used with all arithmetic operators

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Exercise - 1

• Compute volume of an object
• Read in
• Object mass (grams)
• Object density (grams per cubic centimeter)
• Output
• Volume (cubic centimeters)
• Relationship
• Density Mass/Volume

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Code Needs

• Determine variables (with types needed)
• Issue prompts use cout, e.g.
• Cout ltlt Object Mass? ltlt endl
• Read in values use cin, e.g.
• Cin gtgt mass
• Compute Distance and Velocity

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Conditional Expressions

• Any combination of logical and relational
  operators
• Use () as needed
• Examples
• Simple if statement
• if( a lt b)
• s1
• else
• s2

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If/else statement

• General format single statement execution on
  true condition
• Long format multiple statement execution on
  true condition
• General rule more than one statement under if
  and/or else condition requires
• Short-hand format single statement
• Nested if statements

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If single statement

• Format
• if(expression)
• s1
• else
• s2

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If multiple statements

• Format
• if(expression)
• s1
• s2
• else
• s1
• s2

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If shorthand

• Used only with single statements
• Format
• Expression ? S1 s2
• Example
• c ! b ? c b
• Example
• int a,b
• int min a lt b ? a b

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Short-circuit evaluation

• - evaluation terminates with first false
  condition
• - evaluation terminates with first true
  condition
• Done to insure objects can be properly
  manipulated, e.g.
• (i ! 0) ((j/i) gt 5)

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Arrays

• Included in C for backward compatibility with C
• Arrays less popular and class representation of
  lists, especially the vector class more
  frequently used
• Vector class is an example of container classes
  is defined in the Standard Template Library (STL)

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Simple arrays - Declaration

• const int N 20
• const int M 40
• const int MaxListSize 1000
• // Note const qualifier used to denote constant
  values
• //Declaration examples
• int a10
• float cMN
• int ValuesMaxListSize

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Simple Arrays - Referencing

• Array elements are referenced using subscripts or
  indices
• First index in C is 0
• Examples
• a0 b
• ai aj 3
• aak 12
• Warning No automatic checking for array
  boundaries. Illegal subscripts will result in
  inaccurate memory references or storage

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Simple Array - Initialization

• Int frequency5 0,0,0,0,0
• Int total5 0 // first element set to 0,
  remainder are uninitialized and default at 0
• Int digits 0,1,2,3,4,5,6,7,8,9
• Int zero 0 //one-element array

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Iteration

• For-loops
• While-loops

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Iteration using while

• Format
• while (conditional expression)
• s1
• Statement in the block are executed as long as
  condition is true
• If condition is evaluated to false, statements
  are never executed

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Interation using for

• Format
• for (ForInit ForExpression PostExpression)
• ForInit initialization step to start loop
• ForExpression logical expression
• PostExpression next iteration of loop

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For examples

• for( i 0 ilt maxsize i)
• for(jminsize j lt maxsize j2)
• for(k maxsize k gt minsize k--)

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Exercises

• Compute n! using a for loop
• Compute the nth Fibonacci term using a while loop

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• Example, compute roots of a quadratic equation
• //Quadratic roots
• include ltiostreamgt
• include ltstringgt
• include ltmath.hgt
• Using namespace std
• int main()
• double a, b, c
• cout ltlt Coefficients for quadratic equation
  
• cin gtgt a gtgt b gtgt c
• if ((a ! 0) ((bb 4ac) gt 0))
• double radical sqrt(bb 4 a c)
• double root1 (-b radical) / (2 a)
• double root2 (-b radical) / (2 a)
• cout ltlt roots are ltlt root1 ltlt and
  ltlt root2 ltlt endl
• else
• cout ltlt No real roots ltlt endl

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Compute area of a circle

• include ltiostreamgt
• include ltstringgt
• Using namespace std
• const float Pi 3.1415
• int main()
• float radius
• cout ltlt Enter radius
• cin gtgt radius
• //compute area
• float area Pi radius radius
• //output
• cout ltlt Area ltlt area

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More general using functions
include ltiostreamgt include ltstringgt Using
namespace std float CircleArea(float r)
const float Pi 3.1415 return Pi r
r int main() float radius cout ltlt
Enter radius cin gtgt radius //compute
area float area CircleArea(radius)
//output cout ltlt Area ltlt area
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Function prototyping

• Functions cannot be used until they are defined
• Can create problems with functions calling other
  functions
• Use prototype conventions
• Define function prototype before main
• Implement function after main

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Prototype Example
include ltiostreamgt include ltstringgt Using
namespace std float CircleArea(float r) int
main() float radius cout ltlt Enter
radius cin gtgt radius //compute area
float area CircleArea(radius) //output
cout ltlt Area ltlt area float
CircleArea(float r) const float Pi
3.1415 return Pi r r
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Homework

• Write a program for integrating a quadratic
  polynomial
• User input will be
• Quadratic coefficients a1, a2, a3
• Interval of interest n1, n2
• Output will be the area