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36 Cards in this Set
- Front
- Back
Function
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A special type of module whose purpose is performing a specific task.
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What happens when a program finishes?
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The function returns a value back to the part of the program that called it and then can be used like any other value.
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How are values used?
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1. Assigned a variable
2. Displayed on screen 3. Used in a mathematical expression |
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Library Functions
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Built in functions that have already been written into the into the programming language that you can call anytime you need them.
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Benefits of library functions
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Makes programming easier because these functions perform many of the taks that programmers commony need to perform.
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Examples of what library functions do
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manipulate numbers, perform various math operations, convert data from one type to another, manipulate strings, etc.
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What happens when you call a function?
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The compiler/interpreter automatically causes the function to execute without requiring the function's code to appear in your program
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What do you need to know when using library functions?
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1. Purpose of the library function
2. Arguments you must pass to it 3. The type of data it returns |
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Black Box
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Any mechanism that accepts input, performs some operation that cannot be seen on the input, and produces output.
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random Function
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A library function that generates random numbers.
randomize() in vb |
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Uses for the random function
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Useful for simulation programs - formulas can be constructed in which a random number is used to determine various actions and events that take place in the program.
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Calling a random function
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set number = random(1, 100)
When the function is called, it will generate a random number 1-100 and then return the number, which is then assigned to the number variable. |
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Custom Functions
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Essentially modules/subroutines that allow you to send a value back to the part of the program that called it
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Function Header
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1. Specifies data type of returned value
2. Name of the function 3. Parameter variables used to accept arguments |
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Function Body
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One or more statements that execute when the function is called
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Return Statement
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Statement in the body which specifies the value that is returned from the function when it ends.
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Parts of a Function Header
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dataType of return value and function name
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Return Value
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Last line of the body. Value that the function sends back to the part of that calls the function
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How many arguments can you pass into a function?
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As many arguments as you need, but you can only return one value.
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Uses of Functions
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1. Can prompt user for input and then return the value entered by the user
2. Simlify complex mathematical expressions |
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IPO Chart
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Input, processing, output. Describes the input, processing, and output of a function. Used to design functions.
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Uses of Boolean Functions
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Help to simplfy complex conditions that are tested in decision and repetition structures (roulette game, hello!)
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Designing Boolean Functions
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The function accepts a number as an argument and returns "True" if the conditions are true, or "False" if the conditions are otherwise. (cool!)
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Mathematical Library Functions
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Many programming languages offer many mathematical functions in the library.
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Data Type Conversion Functions
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Library Functions that convert values from one data type to another. Example: toInteger. See page 243 for these functions
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Type Mismatch Error
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An error that occurs when a programmer tries to assign a value of one data type to a variable of another data type.
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Length Function
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returns the length of a string
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Append Function
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accepts two strings as arguments and returns a third string that is created by appending the second string to the end of the first string. This is called "concatenation"
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toUpper Function
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accepts a string as an argument and returns a copy of the argument as uppercase
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toLower Function
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same as toUpper but converts the copy to lowercase instead
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Substring Function
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substring is a string within a string and the function returns sections of the string that you wish to call back
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Contains Function
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accepts 2 strings as arguments, returns True if the first string contatins the second string
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stringToInteger Function
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Converts a string to an integer
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stringToReal Function
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Converts a string to an integer
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isInteger Function
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determines whether a string can be converted to an integer
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isReal Function
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determines whether a string can be converted to a real
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