1. Concepts of Programming Languages
Presented by: Dr. Emad Nabil
Fall 2018
Slides by

2. Grading Policy
Task
Percent %
Assignments and MT 40
Final 60

3. Assignments Submission policy
No Late submission.
Plagiarism means grading by –ve marks.
Discussion of assignments is a must. Without discussion No marks will be assigned.

4. Languages
Python
C++
Java C#
Ada
Prolog
Lisp

5. Course Contents Ch6: Data Types Ch8: Subprograms Ch1:Preliminaries
Ch3: Describing Syntax and Semantics
Chapter 5 Names, Bindings, and Scopes
Ch6: Data Types
Ch7: Expressions and Assignment Statements
Ch8:Statement-Level Control Structures
Ch8: Subprograms
Ch13:Concurrency

6. Course Page
All materials will be uploaded to Acadox : GP:

7. Text Book
Other materials on course page +

8. Chapter 1
Introduction

9. Chapter 1 Topics
Reasons for Studying Concepts of Programming Languages
Programming Domains
Language Evaluation Criteria
Influences on Language Design
Language Categories
Language Design Trade-Offs
Implementation Methods
Programming Environments

10. Reasons for Studying Concepts of Programming Languages
Improved background for choosing appropriate languages
Increased ability to learn new languages
Better understanding of significance of implementation
Better use of languages that are already known

11. Programming Domains Systems programming Scientific applications
Large numbers of floating point computations; use of arrays
Fortran, Matlab, Python
Business applications
Produce reports, use decimal numbers and characters
COBOL, Java, Oracle, C#
Artificial intelligence
Symbols rather than numbers manipulated; use of linked lists
LISP, prolog, Python
Systems programming
designing and writing computer programs that allow the computer hardware to interface with the programmer and the user, leading to the effective execution of application software.
performance constrained,
needs hardware awareness
Need efficiency because of continuous use
Examples OS, compilers, interpreters, scheduler.
C/C++
Web Software
collection of languages:
markup (e.g., HTML),
scripting (e.g., PHP),
general-purpose (e.g., Java)
ASP.NET
Python

12. Language Evaluation Criteria
Readability: the ease with which programs can be read and understood
Writability: the ease with which a language can be used to create programs
Reliability: conformance “matching” to specifications (i.e., performs to its specifications)
Cost: the ultimate total cost

13. Evaluation Criteria: Readability1
Evaluation Criteria: Readability
Overall simplicity
Minimal feature multiplicity : having more than one way to accomplish a particular operation is bad.
Minimal operator overloading
Orthogonality
A relatively small set of primitive constructs can be combined in a relatively small number of ways
Every possible combination is legal
Data types
Adequate predefined data types
Syntax considerations
Identifier forms: flexible composition (combining)
Form and meaning: self-descriptive constructs, meaningful keywords

14. Evaluation Criteria: Writability2
Evaluation Criteria: Writability
Simplicity and orthogonality
Few constructs, a small number of primitives, a small set of rules for combining them
Support for abstraction
The ability to define and use complex structures or operations in ways that allow details to be ignored
Expressivity
A set of relatively convenient “easy” ways of specifying operations
Strength and number of operators and predefined functions

15. Evaluation Criteria: Reliability3
Evaluation Criteria: Reliability

16. Evaluation Criteria: Reliability3
Evaluation Criteria: Reliability
Type checking
Testing for type errors
Exception handling
Intercept run-time errors and take corrective measures
Aliasing
Presence of two or more distinct referencing methods for the same memory location dangerous feature in a programming language.
Writability and Readability
Both readability and writability influence reliability
A language that does not support “natural” ways of expressing an algorithm will require 
the use of “unnatural” approaches, and hence
reduced reliability
A program is said to be reliable if it performs to its specifications under all conditions.

17. Evaluation Criteria: Cost (Money and Time)4
Evaluation Criteria: Cost (Money and Time)
Training programmers to use the language
Writing programs (closeness to particular applications)
Compiling/ Executing programs “speed”
Language implementation system: availability of free compilers
Reliability: poor reliability leads to high costs
Maintaining programs

18. Evaluation Criteria: Others5
Evaluation Criteria: Others
Portability
The ease with which programs can be moved from one implementation to anther
A committee began work on producing a standard version of C++ in It was approved in 1998.
Standard versions  (C++ 98, C++11, C++2014, C++2017, C++20,….)
Generality
The applicability to a wide range of applications
Well-definedness
The completeness and precision of the language’s official definition

19. Influences on Language Design

20. Influences on Language Design
Computer Architecture
Languages are developed around the prevalent computer architecture, known as the von Neumann architecture
Program Design Methodologies
New software development methodologies
(e.g., object-oriented software development) 
led to new programming paradigms 
new programming languages

21. Imperative programming Vs. Declarative Programming
Imperative programming languages
focuses on describing how a program operates.
a developer writes code that describes in exacting detail the steps that the computer must take to accomplish the goal. This is sometimes referred to as algorithmic / procedural programming. Ex (C#, Visual Basic, C++, and Java ) 
Declarative Programming languages :
is non-procedural and very high-level (4th generation).
focuses on what the program should accomplish without specifying how the program should achieve the result.
expresses the logic of a computation without describing its control flow.
Declarative programming often considers programs as theories of a formal logic, and computations as deductions in that logic space. EX:
database query languages (e.g., SQL, XQuery),
regular expressions,
logic programming (Prolog),
functional programming (Lisp, Haskell).
Markup languages (NOT Programming language)
It is a document format
Markup languages extended to support some programming (Java script)
Examples: HTML, XML

22. 1-Computer Architecture Influences on Designing programming languages
Well-known computer architecture: Von Neumann
Imperative languages most dominant, because of von Neumann computers
Properties of Imperative languages
Data and programs stored in memory
Memory is separate from CPU
Instructions and data are piped from memory to CPU
Basis for imperative languages
Variables model memory cells
Assignment statements model piping
Iteration is fast on von Neumann computers (faster than recursion)

23. The von Neumann Architecture

24. Von Neumann Bottleneck
Connection speed between a computer’s memory and its processor determines the speed of a computer
Program instructions often can be executed much faster than the speed of the connection; the connection speed thus results in a bottleneck
Known as the von Neumann bottleneck; it is the primary limiting factor in the speed of computers
instructions executed fast
Connection with memory is slow
von Neumann bottleneck