introduction introduction to systems programming - comp 1002, 1402 instructor : behnam hajian...
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INTRODUCTION
Introduction to Systems Programming - COMP 1002, 1402
Instructor : Behnam Hajian
Objectives and syllabus
The objectives in this course is: To expose students to lower level systems
interface only clearly visible via C. To further develop the ability to design
programs with emphasis on the abstract view of data structures.
To get experience with the low-level implementation of data structures in C.
To experience programming in the
Large
Objectives and syllabus (continue)
In this course you will learn: The structure of a C program How to use C/C++ compilers such as MinGW,
Cygwin, GCC,… How to execute a C program by platforms such as
Borland C builder, Netbeans IDE, GCC,… Variables and memory allocation Type conversion, operators control statements in C (if-then-else, while, for) Function and Procedure, Call by Ref. and Call by
Value, Input, Output
Objectives and syllabus (continue)
Header files, System and Library Calls Structs and complex data structure Arrays and String (1-D, 2-D , n-D array) Pointers and more on dynamic memory
allocation, and de-allocation Heap, Stack Linked lists Manipulation
Evaluation and…
5 programming assignments : 50% Final Exam: 50%Website: Course material will be available on WebCT:
look for the WebCT link from Carleton’s web site.
Lectures: Tuesday & Thursday 6PM - 9 PM @ 502
Southam HallOffice hours: The hour before lecture. @ HP 5270 or HP 5336
TextBook
References: PPT slides are the most important
resource for final exam. However, reading the textbook is highly recommended.
TextBook: C How to Program, 5th Edition,
Harvey M. Deitel and Paul J. Deitel, both from Deitel & Associates, Inc.
Computers
What is a computer? A computational device Logical decisions billions of times faster than
humans Hardware
keyboard, screen, disks, memory, CPU Software
email, word processing, spreadsheets, OS
Computer Organization
Input unit keyboard, microphone
Output unit screen, printer
Memory unit Random Access Memory (RAM)
short-term, rapid access, low capacity warehouse Read only memory ROM
Smaller amount of memory stable when power off. Stores enough code to boot system
Computer Organization
Secondary storage unit disks, tapes
long-term, slow access, high capacity warehouse
Central Processing Unit (CPU): Microprocessor (Intel Pentium, Motorola power PC): fetches machine instructions from memory, executes them Arithmetic and logic unit (ALU)
calculations, comparisons CU (Control Unit)
coordinator, administrator,
Computer Architecture
CPU
Program Control Unit
ALU
Memory I/O
Computer Architecture (cont.)
Computing Modes
Batch Processing one job at a time
Multiprogramming many jobs simultaneously
Timesharing multiple jobs, multiple users
Personal computer (PC) standalone units
Distributed computing workload distributed over networks
Client/Server client machine provides user interface server machine provide computational power and
storage location
Programming Languages
Machine Language machine/hardware dependent Too hard to program in
Assembly Language English-like operations (e.g., load, store, add)
High-level languages single statement can accomplish substantial
tasks English-like statements with mathematical
notations
Why C?
Because we have to!C supports: Many situations where it is only language or
system available Small, embedded systems, instrumentation, etc.
Many “low-level” situations that don’t have support for “high-level” languages
Operating systems, real-time systems, drivers
Why not C?
C is very low-level Data structures must be programmed “by hand” e.g. set,collection,
… Operations must be done out in “long hand” No support for “object oriented” design Marginal support for higher-level thought processes Much, much harder to use than higher level languages/systems
Better alternatives available for almost all applications Java, Python, Ruby, etc. – many CS situations Matlab, SimuLink – physical modeling LabView – instrumentation and control Excel – accounting and statistics SQL – billing and transactions …
What about C++?
Object-oriented thinking Data abstractions, classes, objects, interfaces Operator overloading Inheritance Lots of other good stuff …
Backward compatible with C To some extent Allows programmer to get close to hardware when needed Allows programmer to get close to data representation when
needed Not platform independent (like Java) Still need to be conscious of memory management …
C Program Development Environment
Standard Steps1. Edit2. Preprocess3. Compile4. Link5. Load6. Execute
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A Short History
In the beginning … Machine language Assembly language
One line per machine instruction
So “high level” languages were invented Non-recursive:– Fortran, Cobol Recursive:– Algol, Lisp, Snobol, PL/1, etc.
Really primitive!Too difficult for big projects
Too advanced!Too much infrastructure for operating
systems, control systems, manykinds of projects
C: History20
Developed in the 1970s – in conjunction with development of UNIX operating system When writing an OS kernel, efficiency is crucial
This requires low-level access to the underlying hardware: e.g. programmer can leverage knowledge of how data
is laid out in memory, to enable faster data access UNIX originally written in low-level assembly
language – but there were problems: No structured programming (e.g. encapsulating routines
as “functions”, “methods”, etc.) – code hard to maintain Code worked only for particular hardware – not portable
C: Characteristics21
C takes a middle path between low-level assembly language… Direct access to memory layout through
pointer manipulation C is Concise syntax, small set of
keywords Is also a high-level programming
language like Java: Block structure Some encapsulation of code, via functions Type checking (pretty weak)
C: Dangers22
C is not object oriented! Can’t “hide” data as “private” or “protected” fields You can follow standards to write C code that looks
object-oriented, but you have to be disciplined – will the other people working on your code also be disciplined?
C has portability issues Low-level “tricks” may make your C code run well on
one platform – but the tricks might not work elsewhere The compiler and runtime system will rarely stop
your C program from doing stupid/bad things Compile-time type checking is weak No run-time checks for array bounds errors, etc. like in
Java
QUESTIONS?