Lecture 6 Builtin Functions

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Lecture 6Built-in Functions

• ENGR17 Engineering Programming
• Section 1
• Fall 2001

9/21/01
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Outline

• What are functions
• Purpose of functions
• String functions (review)
• Math functions
• Other functions

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Functions

• Blocks of code that perform a specific task
• Allow programmers to write programs quickly and
  easily
• Two Types
• Built-in Functions
• User-Defined Functions
• Some functions that are built into the C
  language
• pow
• strcpy
• Some are created by the programmer
  (programmer-defined functions)
• main
• More next week

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String Functions
All of these functions require include ltstring.hgt
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Purposes of Functions

• Make problem solving easier
• Allow programmers to break large and complex
  problems into small and manageable tasks
• Speed up program writing by allowing programmers
  to use existing code to perform common tasks
• Omit the need for duplication of code in
  different parts of the program(can be used as
  many times as necessary)

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Mathematical Functions

• Defined in the math.h header file
• Can be used by entering the include ltmath.hgt
  directive in the program

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Mathematical Functions
Need math Functions here
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pow Function

• Used to raise a number to a power XN
• Syntax pow(base,exponent)
• Actual arguments (base, exponent) represent
  information that is sent to a function
• Function returns the result as type double
• Need to do a type conversion if you put the
  result of the function into a variable that is
  not a double

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pow Function
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sqrt Function

• Used to calculate the square root of a number
  stored in a variable ?X
• Syntax sqrt(number)
• Returns type double

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Using Math Functions
Add math.h
Use math Functions here
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Other types of functions

• There are many other types of built-in functions
• Input/Output
• Graphics
• Others
• In addition, we can create our own functions
• Next lecture

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Summary

• Understand what functions are and why are they
  used
• Know the 4 string functions and how they are used
• Know the 2 math functions and how they are used

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General Notes on Exam 1

• In Loma 4 (Lecture Room)
• Closed book
• Come early Donuts and Juice starts at 730am
• Types of Questions (total of 100 points)
• Short Answer (about 20 questions worth 2 or 3
  points each)
• 2 or 3 Programs (worth 60 points total)
• What to study
• Class notes
• Questions at end of lectures
• In-class assignments
• Labs
• Homework assignments

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Exam 1 Review

• Lecture 1
• History of PC
• Components of PC
• History of Programming Languages
• Object-oriented languages
• Control Structures
• Lecture 2
• Six problem-solving steps used to create a
  computer program
• Complete an IPO chart
• Plan an algorithm using pseudocode and flowcharts
• Desk-check an algorithm
• Code and execute the algorithm

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Exam 1 Review

• Lecture 3
• Style
• Variables
• Literal Constants
• Select an appropriate name, data type, and
  initial value for a variable
• Create and initialize a variable
• Perform explicit type conversion
• Lecture 4
• Named Constants
• Assignment Statements
• Writing Equations
• Precedence
• Type conversion

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Exam 1 Review

• Lecture 5
• String Data Type
• Declarations
• Individual Characters
• Loading a String Variable
• String Functions
• Reading a String from Keyboard
• Lecture 6
• What are functions
• Purpose of functions
• String functions
• Math functions
• Any other questions????