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

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.

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!

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 - 1958) Education Pascal COMAL BASIC Operating Systems C C++,C#

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!

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!

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

How an interpreter works Nat 4/5 How an interpreter works Original Source Code Pctoutput.isible = true Interpreter Pctoutput.print “Hello” 1001 1000 1100 1110 0011 1001 1000 1100 1110 0011 Syntax Error

Can be saved and ran later Nat 4/5 How the compiler works Can be saved and ran later Original Source Code Pctoutput.isible = true Pctoutput.print “Hello” Object Code Compiler 1010 1010 1010 0111 0011 1001 1000 1100 1110 0011 Syntax Error

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