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APSC 160 Notes
Introduction To Computation In Engineering Design (APSC 160)
The University of British Columbia
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APSC 160 Notes
Fundamentals I
● Comment Statement: ○ Included for the benefit of other programmers + ignored by compiler when the program is translated to machine language. ○ Provides information about who wrote it, when it was written and what program does when its run ● Compiler Directive: ○ Instruction for the compiler rather than an instruction to be executed when the program runs ○ All compiler directives in C start with “#” character ● Header File: ○ Contains declaration of symbols used by our programs ○ Ex. Stdio ■ Includes declaration of “printf” function that is used by our program to print message on screen ● Function: “return 0;” ○ Terminates program, indicates program terminated normally
Fundamentals II
● Abstraction: process of hiding non-essential details and only exposing those aspects of a system we are interested in ● Header File “#define” ○ Used to create symbolic constant. When compiler executes directive, it searches for all instances for symbol listed beside this header file and replaces it with value beside symbol ■ Symbolic constant: makes programs easier to read and maintain. Should be used to represent constant values. Capitalized
Fundamentals III
● Have to end every line with “;” ● Variable declaration: two parts, type of data to be stored in variable and name of variable (data type, variable name) ○ Type of data depends on what variable is being represented for ○ Variable name is chosen by programmer ○ Variables must be declared before they are used in program
● Garbage value: initially variables hold this value. It’s whatever value happens to be stored in memory at that time ● Assignment operator “=” ○ Used to assign value to variable, NOT an equals sign ○ Variable receiving assigned value must be on the left ● Whenever the name of a variable appears in code, it is replaced with the value of that variable. Garbage value is overwritten and cannot be retrieved. Variables can only store one value at any given time ● Format specifier ○ Used in printf function as a placeholder for the value of variable ● “&” ○ Specifies address
Fundamentals IV
● Integer Data Types ○ Can only store integer values in specified range ○ See Fundamentals IV for chart ○ Choose type “int” whenever you want to store integer values ● Unsigned Integer Data Types ○ See Fundamentals IV for chart ○ Only use these if you want to store non-negative values ● Floating Point Data Types ○ Used to store non-integer values ex. 3. ○ Use type “double” to store floating point value ● Character data types ○ Letters ○ Type “char” consumes single byte of memory and is capable of storing a single character ○ middleInitial = ‘A’ ■ Used single quote marks to represent value ● Identifiers in C ○ They must start with a letter of the alphabet or an underscore ○ All other characters must be a letter of the alphabet, a digit, or an underscore
Fundamentals V
● Unary operator ○ Only takes one operand (negative) ○ Ex. y = -x ● Binary Operator ○ Takes two operands ○ Addition, subtraction, multiplication, division, remainder (%)
Fundamentals VIII
● All functions in C have common characteristics ○ Have a name ○ 0 or more parameters (inputs) ○ 0 or 1 return value (output) ● Abstraction: details of how a function works hidden from programmer who uses function ● Function interface: what functions name? ○ Programmer must understand this ● If function does not take any parameters, its list is specified as void ○ Ex. int main(void) ● If function doesn’t return a value, then return type is void ○ Ex void main( void ) ○ No return statement because it doesn’t return anything
Flow of Control I
● Algorithm: an unambiguous sequence of step-by-step instructions for solving a problem ○ Basically a sequence of instructions ● Can be specified graphically ○ Using a flowchart ● Algorithms can consist of ○ branching/selection: where one sequence of instructions is executed if some condition is true and another if its false ○ looping/repetition: where a sequence of instructions is repeated for as long as some condition is true ● Boolean Expression: an expression whose value is either true or false ● “Repeatedly” ○ Algorithm has a loop ● See Flow of Control I for more details
Flow of Control II
● “!=” not equal to ○ Unary operand ● “Count % 2 == 0” ○ Determine if count is even integer ● “&&” if both operands are true ○ Binary operand ● “||” only one operand has to be true
○ Binary operand ● Helpful to draw table ● See Flow of Control II for precedence of operands
Flow of Control III
● See Flow of Control III for simple branching code
Flow of Control IV
● Nested Branching: ability to put a branch inside of another branch ○ Can be in true block, false block, or both ● Symbolic constants are useful in updating program if specifications change ● Side by side branches make layout more neutral ● Preferred branching code found on Flow of Control IV ● Braces “{}” are optional when block contains single statement ● See Flow of Control III for nested branching code
Flow of Control V
● Simple pre-test loop: Boolean condition tested before body of loop is executed ○ Body of loop contains statements that will be executed ONLY when Boolean expression is true and will keep executing WHILE Boolean expression is true ● Use trace table to keep track of loops ● See Flow of Control V for simple loop code
Flow of Control VI
● If no change in variable, there can be an infinite loop ● An error in Boolean expression can also result in an infinite loop ● “Do While” loops ○ Execute function first then ask whether user wants it to continue ● See Flow of Control VI for do while loop code
Flow of Control VII
● If they want a grid printed, increment rows in outer while loop ● Nested looping: when one loop is wrapped inside another one ● Generally redefine value at start of outer while loop, before inner while loop ● Figure out what outer while loop needs to execute then figure out inner while loop, work in modular increments ● See Flow of Control VII for nested loop code and for while if code
APSC 160 Notes
Course: Introduction To Computation In Engineering Design (APSC 160)
University: The University of British Columbia
