4.6 - Computer Systems Flashcards
Low Level Languages
Machine-dependent. Instructions reflect exactly how the code is carried out on a computer.
Machine Code
Instruction are formed in binary of an opcode and an operand. The first x bits of an instruction would represent the opcode and the latter the operand. No need for translation.
Assembly
Opcode represented as a pneumonic and the operand a decimal/hexadecimal a number or register. Each instruction has a 1:1 correlation with a machine code instruction. Must be assembled.
Imperative High Level Language
Each instruction specifies HOW a computer should execute a certain step of a program.
Compiler
Translates the program all at once.
Produces an executable file.
Faster than the other one.
More secure (harder to reverse engineer).
Interpreter
Translates line-by-line.
Helps when debugging to find syntax errors.
Intermediate Bytecode
Combines the benefits of interpretation and compilation.
Allows for platform independence as the bytecode is run by a VM on a device.
Advantages of HLLs over LLLs
+ Easier to learn.
+ Simpler and faster to write code in.
+ Easier to understand and debug.
+ Platform independence can be achieved.
+ Lots of built-in functions avaliable.
Hardware
The physical parts of a computer.
Software
Programs written for the computer.
Systems Software
Required for the computer to function.
e.g. OS, utility programs, translators.
Operating System
Manages all computer hardware. Some also create a GUI for a better user experience.
Utility Programs
Designed to carry out a specific function. e.g. disk defragmentation or compression.
Libraries
Ready-compiled programs that can be run when needed (think Python libraries).
Application Software
Programs that perform user-oriented tasks.
General-purpose Software
Able to perform many different tasks e.g. Word Processor
Special-purpose Software
Perform a specifc set of tasks e.g. bookings system.
Bespoke Software
Perform highly specific tasks e.g. a piece of software that was made for one company to do one thing.
Functions of the Operating System
Memory management, processor scheduling, backing store management, peripheral management.
Half-adder circuit
Both A and B go into an XOR and an AND gate. The XOR outputs the sum and the AND outputs the carry.
