national 5 computing science

readabilty

programmers do this so that other people can understand the code and maintain it if necessary this can be done through meaningful variable names,internal commentary or white spacing

calculating filesize

take the length time dpi then take the height and times that by the dpi then times them together after that you times by the color depth then divide by 8 this makes the answer in bytes then divide by 1024 till you get a suitable number(remember to include units)

loops

there are two types of loops conditional and fixed. a fixed loop is when you have a piece of code that you want the computer to repeat a set number of times.a conditional loop is when you have a piece of code repeating till it meets the condition required to proceed

predefined functions

predefined functions are sections of code that have been written, tested and saved in a library for later use most popular are len-calculates no. of characters in a word

ucase- coverts string into uppercase

lcase-coverts string into lower case

testing

testing- allows a programmer to check his/her program to make sure all functions are working three are three main types of testing

-normal-testing the data within the limits

-extreme-testing the data at its limits

-exceptional-testing data over its limits

ascii

american standard code for information interchange- ascii is a seven bit code which provides 128 code values

RAM:random access memory

-the processor can write to or read from ram at high speed

-data held in ram can be changed

-all data in ram is lost when the power is switched off

-ram holds all the data and programs currently in use

ROM:read only memory

data is stored permanently stored in ROM

data in ROM can not be changed

ROM holds vital systems data and programs

busses

buses are used as transmitters between the different parts of a computer system.the three main buses are the data bus,address bus and the control bus

control unit

this sends control signals which allow data to be stored and fetched from memory and which decodes and carries out instructions

arithmetic and logic unit

this carries out all of the computer's arithmetic and logical functions such as addition subtraction multipication and comaring values

registers

stores data that is being transferrend to or from memory

interfaces

an interface is the combination of hardware and software needed to link the processor to peripherals,and is the means by which independent systems can communicate,despite their differing characteristics

unicode

16 bit code which supports 65536 characters which allows it to:

-use every alphabets in the world

-use languages such as Chinese Japanese and Korean

interpreter

it translates each line of code every time the program is run

compiler

translates code once and is never needed to be done again unless changes have been made

machine code

machine code is the language each computer around the world understand but is very difficult to read so we use high level languages to code