1. Nat 4/5 Computing Science Translator Programs
Computer Systems
Nat 4/5 Computing Science
Translator Programs

2. Lesson Aims By the end of this lesson: All pupils will be able to:
Describe and compare the following types of languages:
Machine Code
High Level Languages
Describe why High Level Languages require translation.
Describe how interpreters and compilers function.

3. Types Of Languages Machine Code is made up of only 2 symbols.
Nat 4/5
Types Of Languages
Machine Code is made up of only 2 symbols.
1 and 0 (On and Off)
High Level Languages such as Visual Basic are written using some English words.
They are not written IN english!

4. Artificial Intelligence
Nat 4/5
High Level Languages
General Purpose
Pascal, C, C++ and COMAL
ALGOL (Initially used for Mainframes)
Artificial Intelligence
PROLOG (PROgramming in LOGic)
LISP (Probably 2nd oldest language still in use )
Education
Pascal
COMAL
BASIC
Operating Systems C
C++,C#

5. Nat 4/5
Why do we need them?
The source code you write is instructions for the computer
They are in a High Level Language
The computer needs these instructions translated into machine code
It’s the only language it understands!

6. Nat 4/5
Types of Translators
These programs convert High Level Language Source code into machine code (binary)
Interpreter
Translates and executes one line at a time
Compiler
Translates and executes the entire program at once
This program can then be ran repeatedly
Think complete!

7. Interpreter Functions like a spoken language interpreter.
Nat 4/5
Interpreter
Functions like a spoken language interpreter.
Translates and executes a single line at a time
The interpreter is ALWAYS loaded in memory
Error feedback is provided line by line
Like in Smallbasic
Interpreted programs have to be re-interpreted every single execution

8. How an interpreter works
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How an interpreter works
Original Source Code
Pctoutput.isible = true
Interpreter
Pctoutput.print “Hello”
Syntax Error

9. Can be saved and ran later
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How the compiler works
Can be saved and ran later
Original Source Code
Pctoutput.isible = true
Pctoutput.print “Hello”
Object Code
Compiler
Syntax Error

10. Nat 4/5
Summary
Compilers translate source code once into an executable program
Only has to be translated once!
Cannot see the source code in a compiled program
Interpreters translate source code line by line
Always has to be re-interpreted
Spots errors line by line