Introduction Programming with C CSCI 112, Spring 2015 Patrick - - PowerPoint PPT Presentation

Introduction

Programming with C

CSCI 112, Spring 2015

Patrick Donnelly

Montana State University

Introduction

What is Computer Programming?

Programming with C (CSCI 112) Spring 2015 2 / 15

Introduction

What is Computer Programming?

• problem-solving or “puzzle solving”

Programming with C (CSCI 112) Spring 2015 2 / 15

Introduction

What is Computer Programming?

• problem-solving or “puzzle solving”
• translation of a problem to an executable computer program

Programming with C (CSCI 112) Spring 2015 2 / 15

Introduction

What is Computer Programming?

• problem-solving or “puzzle solving”
• translation of a problem to an executable computer program
• designing, writing, testing, debugging, and maintaining the

source code of computer program

Programming with C (CSCI 112) Spring 2015 2 / 15

Introduction

What is Computer Programming?

• problem-solving or “puzzle solving”
• translation of a problem to an executable computer program
• designing, writing, testing, debugging, and maintaining the

source code of computer program

• combination of high-level design and low-level implementation

details

Programming with C (CSCI 112) Spring 2015 2 / 15

Stages of Problem Solving

Goal: use a computer to solve a problem Typical stages of building a solution:

1 Specify the problem 2 Analyze the problem 3 Design an algorithm to solve the problem 4 Implement the algorithm (write the program) 5 Test and verify the completed program 6 Maintain and update the program

Programming with C (CSCI 112) Spring 2015 3 / 15

Low Level vs High Level Languages

High Level Languages

• Uses algebraic expressions and symbols from natural languages.
• These languages are human-friendly and farther from machine

language.

• Examples: C, Java, Python

Assembly Language

• Uses mnemonic codes to represent machine language instructions.
• This is a low-level language, very close to machine language.

Machine Language

• A collection of 0’s and 1’s that can be interpretted by the processor.
• There is a different machine language for every processor family.

Programming with C (CSCI 112) Spring 2015 4 / 15

Code Examples

C Code Assembly Code Machine Code (Hex Representation)

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Review: Bits and Bytes

BIT

• Name comes from BInary digiT.
• It is either a 0 or a 1.

Byte

• A collection of bits big enough to represent a single character.
• Typically bytes consist of 8 bits.

Example

10110101 11010010 10010100 10100110 11010010 10100110 A B C D B D

Programming with C (CSCI 112) Spring 2015 6 / 15

Review: Memory Cells

There are many different types of memory available in a computer system. Regardless

• f the type, we can view the memory as an

array of addressable cells.

• A memory cell is an individual storage

space in memory.

• The address of a memory cell can be

thought of as an index into this memory array.

• The contents of a memory cell is the

data stored at that location.

Programming with C (CSCI 112) Spring 2015 7 / 15

Review: Memory Cells

Every memory cell always has content.

• The content of a cell can either be a

program instruction or data.

• We as programmers are required to

correctly interpret memory cell contents.

Example Cell Contents

• 285
• -29.6
• 0.02
• T
• $
• MOV

Programming with C (CSCI 112) Spring 2015 8 / 15

C Language

Designed by: Dennis Richie Appeared in: 1972 Bell Labs Paradigm: imperative Extension: .c, .h Influenced by: ALGOL, Assembly, PL/I, FORTRAN Features: powerful set of operators poor type checking fast run time performance useful for lower-level systems programming unchecked access to computer memory Domains: designed as a systems language used in many application areas Contributions: syntax influence is pervasive

Programming with C (CSCI 112) Spring 2015 9 / 15

C gcd Function

int gcd_iter(int u, int v) { int t; while (v) { t = u; u = v; v = t % v; } return u < 0 ? -u : u; /* abs(u) */ }

Programming with C (CSCI 112) Spring 2015 10 / 15

The C Programming Language

Features

• Low-level access to computer memory via machine addresses.
• Low-level (bit-wise) programming available.
• Good compilers for all platforms.
• Libraries provided by American National Standards Institute (ANSI).

Implications

• The resulting machine code is compact, efficient, and natively run.
• Programs can be extremely fast, and as a result is the most

commonly used language for writing system software.

• C places a lot of trust in, and provides freedom to, programmers.
• C does not protect you from yourself, so be careful!

Programming with C (CSCI 112) Spring 2015 11 / 15

What C Does Not Do

• No Objects (but they are in C++)
• No native support for multithreading and networking

(although there are popular libraries for these).

• No standard libraries for graphics and other (now common)

programming needs.

• Limited error detection.
• No garbage collector.
• No bounds checking of arrays and allocated memory segments.
• No standards for exception handling.

Programming with C (CSCI 112) Spring 2015 12 / 15

Compiling

Compilation: The process of translating the source code (high-level) into executable code (machine-level). Source File: A file containing the program code. A compiler turns the Source File into an Object File. Object File: A file containing machine language instructions. A linker turns the Object File into an Executable File. Executable File: This is the binary file readable by the machine. This is what is typically referred to as the “program”.

Programming with C (CSCI 112) Spring 2015 13 / 15

The Compiler

Integrated Development Environment (IDE)

• IDE’s allow you to edit code and compile in the same environment.
• Editing/debugging features to make programming easier.
• Commercial IDEs like Visual Studio and Borland can be expensive.
• There are open source projects like Eclipse and Netbeans that

usually work quite well.

• We will not use an IDE for this course.

The GCC Compiler

• We will be using the GCC command line tool for this course.
• GCC is a free and extremely powerful C compiler.
• It has been optimized for years and is quite simple to use.

Programming with C (CSCI 112) Spring 2015 14 / 15

Programming with C (CSCI 112) Spring 2015 15 / 15