Programming language classification

• What are the two classifications of programming languages?

  Low-level and high-level languages
• What are the two types of low-level languages?

  Machine-code and assembly language
• What is an imperative high-level language?

  A language that consists of commands for the computer to perform
• What are the advantages of machine-code and assembly language programming compared to high-level programming?

  They offer more control over hardware and can be more efficient
• Who developed the Colossus Mark 1 computer?

  Tommy Flowers
• In what year was the Colossus Mark 1 built?

  1943
• What was the input method for the Colossus computer?

  A continuous loop of paper tape with 20,000 5-bit characters
• How was the Colossus programmed?

  Using switches and plug panels
• What was the output method for the Colossus computer?

  An indicator lamp panel
• What was the purpose of the Colossus during World War II?

  To break the Enigma Code used by the Germans
• What type of cipher was used in the Enigma Code?

  A Vernam-type cipher
• What was the significance of the urgency in breaking the Enigma Code?

  It led to Britain's best brains being recruited to develop hardware and software
• What was the typical memory cell in early computers made of?

  A vacuum tube the size of a light bulb
• What components did early computers have?

  A control unit and an accumulator
• How were early computers programmed?

  Using machine code entered with a series of switches
• What does a typical instruction in machine code consist of?

  An operation code (opcode) and an operand
• How many different instructions are possible using 8 bits for the opcode?

  256 different instructions
• What is the largest value of the operand that can be held in 16 bits?

  65,535
• What is an instruction set?

  All the instructions that a computer can understand and execute
• What does the opcode 0000 do in machine code?

  Loads the value stored in memory location specified by the operand into the accumulator
• What does the opcode 0001 do in machine code?

  Stores the value in the accumulator into memory location specified by the operand
• What does the opcode 0010 do in machine code?

  Adds the value specified in the operand to the value in the accumulator
• What does the opcode 0011 do in machine code?

  Compares the contents of the accumulator with the contents of the location specified by the operand
• What are the two major improvements that assembly language introduced over machine code?

  • Each opcode was replaced by a mnemonic
  • The operand was replaced by a decimal (or hexadecimal) number
• What is the relationship between assembly language and machine code instructions?

  There is a one-to-one correspondence between them
• What does the instruction LDA do in assembly language?

  Loads the value stored in memory location specified by the operand into the accumulator
• What does the instruction STO do in assembly language?

  Stores the value in the accumulator into memory location specified by the operand
• What does the instruction ADD do in assembly language?

  Adds the value specified in the operand to the value in the accumulator
• What does the instruction CMP do in assembly language?

  Compares the contents of the accumulator with the contents of the location specified by the operand
• What does the sample program do in assembly language?

  1. LDA 13: Load the accumulator with the value at memory address 13
  2. ADD 14: Add the value at memory address 14 to the accumulator
  3. CMP 15: Compare the accumulator with the value at memory address 15
  4. BGT 6: If greater, branch to instruction at line 6 (STOP)
  5. STO 15: Store the accumulator value into memory address 15
  6. STOP: End the program
• What advantages does assembly code bring to programmers?

  It is much easier to write, understand, and debug
• What is a disadvantage of assembly code?

  It has to be translated into machine code by an assembler
• What was the first high-level programming language invented?

  FORTRAN
• How do FORTRAN statements compare to machine code?

  They look like Maths or English
• What is the difference between imperative and declarative languages?

  Imperative languages consist of commands, while declarative languages focus on what the program should do
• Name some examples of high-level languages.

  FORTRAN, Pascal, Delphi, Visual BASIC, Python
• What does it mean for a language to be high-level?

  It allows programmers to think in terms of algorithms rather than hardware execution
• What must happen before a high-level program can be executed?

  It must be converted into machine code
• What is a key difference between assembly language and high-level languages?

  Assembly language has a one-to-one relationship with machine code, while high-level languages do not
• What are the advantages of high-level languages over low-level languages?

  They are easier and faster to write, debug, and maintain