programming exam prep

set of instructions for accomplishing a task

• 1. write clear unambiguous instructions
• 2. write in a language that is understood

true or the power being on

false or the power being off

time consuming and prone to cause errors

• - not required by the compiler 
• -essential for readers to understand program 
• - cant have a comment within a comment
• - /*comment*/
• -minimum code should have one comment telling the reader what the program is intended to do the date and the author

- tell the compiler witch sets of eextra commands (functions to permit the user to use ) example standard IO

each statement must end in a semicolon

• is a description of a computer program or algorithm 
• -uses conventions of computer programming 
• -written for humans to read rather than machines

• commands given to the compiler
• always stars with #sign 
• example #include <stdio.h>
• tells the program to include the contents the program its making -- user telling the compiler to use it

• a function is just a program that returns a value 
• every c program must contain one function 
• that is the function that is executed when the program is run

• -used to store values
• -must be a type and must be written (it float double char)
• -example:
• Int number;

To assign a value to the variable

number = 4;

int area; variable declaration

• int area= 1; 
• called initializing a variable

type shows how much memory to store for the variable

ultimately all data is stored as numbers

• the name of the variable 
• rules: 
• not to short or too long

readers should be able to know what its used for

use camel case

example

camelCase

don’t start with capital or number

no blanks commas or special characters

may contain letters underscores or digits

must start with a letter not a number or underscore

case sensitive

don’t choose similar identifiers that differ by case

• -combinations of constants and variables and function calls
• -have both value and type
• -can have logical conditions that are true or false 
• - has some operator (=<>)

+-/*

only has one argument

two operands one on each side of the operator 

%remainder “modulo”

&& and

|| or

<= less than or equal to

>= greater than or equal to

? conditional operator

used to change the value of a variable

value of a variable is replaced with the value of an expression

computable set of steps to achieve a desired result

• 1.     
• Identify the program requirements

• 2.     
• Investigate the problem

• 3.     
• Problem analysis

• 4.     
• Designm the algorithm

• 5.     
• Implement the algorithm

• Some operator create expressions that return
• only  a true or false value 
• n  Needed when
• computer needs to know whats next

n  True (1)

n  False (0)

n  && and

n  || or

• n  ! not causes expression
• that is true to be false and vice versa

if (expression) statement;

statements surrounded by braces

• a multiway conditional
• statement that generalizes the if-else statement
• - use it when there are multiple if statements
• -   1 switch (expression)
•    2 {
•    3     case label1: statement1;
•    4     case label2: statement2;
•    5     ...
•    6     case labeln: statement;
•    7     default: defaultStatement;
•    8 }

cases are based on the value of the expression

• a variable whose value just happens to be a memory address
• -position in memory called address
• -manipulate the values stored at specific memory addresses
• -strings are pointers 
• int *x, y=24;
• x=&y
• x is assigned the location of the variable y in memory 
• *-- extracts the address of y NOT THE VALUE

• *x=&y DOES NOT WORK
• use scanf ("%d", &*X);
• or scanf("%d",x);

• when using scanf dont use & to read the string
• char word[20];
• scanf("%s", word);

char *jedi = "Mara Jade";

cant alter the string -- segmentation fault

• prevent the program from compiling
• violates grammar rules for the C language

• prevent the program from running correctly in all situations
• doesnt do what you want it to 
• examples
• infinite loop
• misunderstanding operator precedence

• use temporary printf statements to check the output 
• helps you tell which part is working and which needs debugging

• errors occur when you run a program 
• two types:
• logic errors 
• fatal errors

• when the executable crashes 
• stack overflow
• divide by zero etc

for loop

• while 
• do while

• number of passes through the loop is known in advance 
• 1 for (expr1; expr2; expr3) 
• 2  statement;

expr1 initialize some parameter (control variable loop variable or index)

expr2 is the condition that must be true for the loop to continue 

expr3 is used to modify the value of the control variable initially assigned by expr1

• loop within a loop 
• executed form the inside out 
• 1 for (i = 1; i <= 4; i++)  
• 2 {  
• 3    for (j = 1; j <= 5; j+=2)   
• 4    {   
• 5       k = i + j;   
• 6       printf("i=%d, j=%d, k=%d", i, j, k);   7    }   
• 8 } 
• In the example above, i is the outer loop counter and j is the inner loop counter. The outer loop is executed 4 times, when i =1,2,3, and 4. For each i value the inner loop is executed 3 times. Since j=1,3, and 5 the inner loop is executed 4*3 or 12 times.

• situations in which the number of passes is not known in advanced 
• while (expression)   
• 2  statement;

• expression represents a condition that must be met
• repeats until expression is not true

• statement must include something that alters the expression to avoid infinite loop
• can have nested loops
• loop control variables should be integers

can be used to provide an early exit from for while a and do loops

the continue statement causes the current iteration of a loop to stop and the next iteration to begin immediately

will execute at least once

• 1. learnability -- user can learn how to accomplish the basic task the first time that the software is used
• 2. efficiency -- quick and minimum effort from the user
• 3. memorability -- user can remember how to use it 
• 4. errors - software is usable if user makes errors 
• 5. satisfaction -- pleasant and enjoyable to use
• 6. utility -- high utility when it provides the features needed to do the tasks

is not exact

when large number may cancel out the smaller number

very small computational result is represented by a zero

a error which results from an attempt to represent a computional relut that is too large to fit into the storage type

• expression is being evaluated 
• ex int converted to double 
• going from d to i is okay
• going from i to d loses info

explicit conversion

self contained program segment that carries out some specific tast

• header (including parameter declarations
• body of the function )

• general form 
• 1 function_header  
• 2 {   
• 3     functionBody   
• 4 }
• 

data type that can hold multiple vaues