C1: Intro Prog Concepts/Von Neumann Model

Question 1

What does memory consist of in the von Neumann Model.

Answer 1

Memory consists of addressable memory
cells (usually one byte per cell) which can
be read and written freely by a program

Question 2

What is a program in the von Neumann Model?

Answer 2

A program consist of (binary) commands
(or instructions) that are stored in memory
and can be loaded by the CPU

Question 3

What is data in the von Neumann Model?

Answer 3

Data is also stored in memory and can be

loaded or stored by commands

Question 4

How is a program executed by the CPU in the von Neumann Model?

Answer 4

A program is executed by the CPU sequentially by
1. loading a command from memory,
2. executing it (e.g. adding two data items), including
loading data from memory and storing results,
3. loading the next command,
4. etc.

The address of the next command (i.e. where to find it
in memory) is stored in the instruction counter register
 (Conditional) Jump commands can be used to explicitly
set the command counter and thus change the control
flow

Question 5

What is procedural programming?

Answer 5

a program is structured
into smaller sub programs (procedures / functions),
which can be called by other procedures

Question 6

What is structured programming?

Answer 6

in addition to calling
procedures there are only three control structures: (1)
sequence, (2) iteration (WHILE), (3) selection (IFTHEN-ELSE)
 Object oriented programming: a program consi

Question 7

What is OOP?

Answer 7

a program consists of
objects that communicate by sending and receiving
messages

Question 8

What is an ‘attribute’ in Programming languages?

Answer 8

The set of properties that characterize all language constructs (e.g. variables,
types, procedures, objects). Ex: common attributes of variables: value
 name
 scope
 address
 type
 lifetime
 mutability

Question 9

What are language constructs in programming?

Answer 9

Syntax and semantics. ex:  integer variable definitions, if-then-else
control structures, class declarations, etc

Question 10

What is a binding in a prog. lang.?

Answer 10

The process of assigning a value to an

attribute is called binding.

Question 11

What are the types of bindings in a prog lang.?

Answer 11

static (before runtime) or dynamic (at runtime)

Question 12

Name an abstraction of memory transformations.

Answer 12

operators (specifies memory transformations)

Question 13

Name some abstractions of a sequence

Answer 13

Control structures and subprograms

Question 14

What is a compiler?

Answer 14

Compiler generates code from program
• Can perform correctness checks in the process
• Can optimise generated code, e.g. for multi-cores
• Generated code can be executable code,
intermediary code, or a program in another language
(trans-compiling),
ex: C, C++

Question 15

What is an interpreter?

Answer 15

Interpreter reads program instructions and
executes them directly
• Example: classical BASIC interpreter, script
languages
• Often more ‘dynamic’

Question 16

What is a Just in Time Compiler?

Answer 16

Just-in-time compiler is a way of combining compiler and interpreter:
• Reads, executes and analyses program instructions
• Performs code optimizations at runtime

Question 17

What is a linker?

Answer 17

In addition to a compiler, the linker combines several compiled program parts. ex: C, C++

Question 18

What is a loader?

Answer 18

In addition to a compiler, the loader loads program into memory, assigns actual
addresses (typically part of OS or shell), ex: C, C++

Question 19

What is a language runtime?

Answer 19

In addition to a compiler, the language runtime provides additional code to execute a program on a concrete machine.

 Handles program initialisation and clean-up
 Performs necessary runtime checks
 Manages error handling
 Performs dynamic memory management
 Usually realised as a combination of compiler generated code, libraries and OS calls
 Different languages provide different runtime
environments!
• Java: very powerful (Java Virtual Machine)
• C: minimalistic