Design, Testing and Translators

Structured programming decomposes the program that you want to write into manageable modules. Each of these modules is then decomposed even further into smaller modules and eventually into modules that perform individual tasks

1) coding is easier because you’re only writing subroutines that carry out very simple tasks 2) lots of programmers can work on one program as each module can be written independently 3) it’s easier to test structured programs as each module can be tested individually 4) individual subroutines and modules can be fixed and updated without affecting the rest of the program 5) you will be able to reuse the subroutines and modules in programs you write in the future

1) comments are useful for explaining what the key features of a program do 2) indentation can be used to separate different statements in a program 3) variables, subroutines and parameters should be named so that they refer to what they actually are 4) only use global variables when necessary as they could affect the rest of your code

Authentication can confirm the identity of a user before they’re allowed to access certain pieces of data or features of the program

Authentication is used to improve security

1) force users to use strong passwords and get them to change their passwords regularly 2) limit the number of failed authentication techniques before access to an account is lost 3) ask for a random selection of characters from the password on each authentication

Checking if data meets certain criteria before passing it into the program

1) range check 2) presence check 3) format check 4) look-up table 5) length check

When the compiler or interpreter doesn’t understand something you’ve typed because it doesn’t follow the rules or grammar of the programming language

When the compiler or interpreter is able to run the program but the program does something unexected

Compilers and interpreters won’t pick them up

1) normal (typical) data 2) boundary (extreme) data 3) erroneous data

Dry running a subroutine or algorithm to make sure there are no logic errors

The amount of time it takes an algorithm to complete a task

Low-level code that represents how computer hardware and CPUs understand instructions. It is represented by binary numbers

Low-level programming language closely related to machine code

000000 00010 00011 00100 00000 100000

ADD r4, r3, r3

1) one instruction represents many instructions of machine code 2) the same code will work for many different machines and processors 3) the programmer can easily store data in lots of different structures without knowing about the memory structure 4) code is easy to read, understand and modify 5) must be translated into machine code before a computer is able to understand it 6) you don’t have much control over what the CPU actually does so programs will be less memory efficient and slower

1) one instruction of assembly code usually only represents one instruction of machine code 2) usually written for one type of machine or processor and won’t work on any others 3) the programmer needs to know about the internal structure of the CPU and how it manages the memory 4) code is very difficult to read, understand and modify 5) commands in machine code can be executed directly without the need for a translator 6) you control exactly what the CPU does and how it uses memory so programs will be more memory efficient and faster

1) assemblers 2) compilers 3) interpreters

To turn assembly language into machine code

To turn high-level code into machine code

1) translates all of the source code at the same time and creates one executable file 2) only needed once to create the executable file 3) returns a list of errors for the entire program once compiling is complete 4) once compiled the program runs quickly, but compiling can take a long time