The Analytical Engine Module 6

1. The Analytical EngineModule 6 Program Translation

2. The Binary Machine • Computers store their programsandinformation in binary code. • A program must be understandable to both the user and the machine.

3. The Binary Machine • Translation from high-level language (English) to low-level language (binary) is accomplished through a program: • Compiler • Interpreter • Assembler • High-level  Low-level • Source code  Object code

4. The Binary Machine • All computers have a hard-wired instruction set that is unique to a specific microprocessor. • Therefore, compilers, interpreters, and assemblers must be written for a specific machine.

5. The Binary Machine • An instruction is a unique set of binary patterns that cause the circuitry of the machine to behave in a certain way. • These circuits are etched into the microprocessor chip.

6. Binary Representations • Binary architecture • Bit – Binary Digit • Nibble(?) – 4 bits • Byte – 8 bits • Word – 2 bytes – 16 bits (at least)

7. Binary Representations • Most modern desktop PCs and Macs measure their memory size in bytes. • 1 MB = 1 million bytes • 12 MB = 12 million bytes or 96 million bits! • 1 GB = 1 gigabyte or 1 billion bytes.

8. Binary Representations • To a computer, binary digits can represent: • Simple binary code • Integers - 0000 0000 0000 0010 = 2 • Integers – 0111 1111 1111 1111 = 32767 • Real Numbers (32 bits) – sign(1 bit), Exponent (8) bits, Mantissa (23 bits)

9. Binary Representations • To a computer, binary digits can represent: • Binary Coded Decimal Numbers (BCD) • 0000 0011 0001 0110 = 316 • Hexadecimal Numbers (Hex) • 1111 0101 0011 1011 = F53B

10. Binary Representations • To a computer, binary digits can represent: • ASCII Code • 0100 0001 = “A” • 0010 0001 = “!” • Check ASCII table handout. • Adopted so computers could represent character (non-numeric) data.

11. Binary Representations • Instruction Codes • Arbitrary – Ex. Is PIPPIN • 0001 0100 = LOD (Load accumulator) • 0000 0101 = STO (Store accumulator contents) • A 256-instruction set can be encoded in 8 bits. • Trend was to richer instruction sets. • Trend now to reduced instruction sets.

12. The Binary Machine • Observe the demonstration of the PIPPEN machine carefully.

13. A Simple Computer • RAM – Random Access Memory • Data – 8, 16, 32 bits • Instructions • 8-bit instruction code • 8-bit address • PC – Program Counter • Keeps address of current instruction

14. A Simple Computer • Accumulator • Special memory location that stores intermediate results of computations. • IR – Instruction Register • Holds a copy of the current instruction to be executed. • Decoder • takes a single input and transfers to multiple outputs.

15. A Simple Computer • MUX – Multiplexor • Routes multiple inputs to a single output. • ALU – Arithmetic Logic Unit • Performs mathematical operations on its input.

16. Assembler – translates mne-monic represen-tations of instructions into binary code. (LOD, ADD, SUB, STO, etc.) Very fast Programmer is responsible for data storage One instruction – One operation correspondance A Simple Computer

17. Language Implementation • Scanning – breaking a string of characters into meaningful pieces called tokens. • W=X–Y; • Like breaking down a sentence into words.

18. Language Implementation • Parsing – Arranging tokens into a sensible logical structure. • W = X + Y * Z; • E1 = Y * Z • E2 = X + E1 • E2  W • Result is called a Parse Tree. • Code Generation – generating one or more machine language instructions based on the Parse Tree.

19. Language Types • Interpreted Languages • BASIC, LISP, JavaScript • Program LineInterpreterBinary CodeExecution • Next LineInterpreterBinary CodeExecution • Fairly slow • Lines translated repeatedly • One line may generate multiple instructions, some unnecessary • User does not need to know details of the machine. Programs run on any machine that has the interpreter.

20. Language Types • Compiled Languages • COBOL, FORTRAN, C, C++, Java • Entire programCompilerBinary CodeExecution • Fairly fast after compilation • Better error detection. • Object program can be stored and run repeatedly without recompilation. • User does not need to know details of the machine. Programs run on any machine that has a compiler.

21. Language Groups • Imperative – fundamental unit is the procedure which is called by a main program. • Pascal, FORTRAN, Ada • Functional – processes are defined in terms of functions with no main program. • LISP

22. Language Groups • Declarative – Input/Output oriented; limited procedure/function support. • COBOL, Prolog • Object-Oriented – processes controlled by “events” which communicate with “objects” via “messages”. • C++, Smalltalk, JavaScript, Java

23. Syntax & Semantics Data Types Strongly Typed Weakly Typed Data Structures Arrays Lists Decision statements IF IF – ELSE Control Statements FOR WHILE WHILE – DO Language Design

24. Language Implementation • Generating Code • Observe the demon-stration carefully. • Check the course web page and then complete Lab 6.3.

25. Language Generations • First Generation – machine language • Second Generation – assemblers • Third Generation – interpreted and compiled languages. • Fourth Generation – object-oriented languages

26. Language Implementation • Symbols & Bits • Observe the demon-stration carefully. • Check the course web page for special instructions. • Complete Lab 6.4.

27. The End Program Translation