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Mastering Engineering Programming: Understanding Variables and Expressions

Dive into the world of programming in engineering with this course on using variables, constants, and expressions in C++. Learn the fundamentals of working with data types, operations, and functions. Explore practical examples and exercises to sharpen your programming skills. Discover how to differentiate between variables and constants, and optimize your code for efficiency. Enhance your problem-solving abilities and gain a solid foundation in engineering programming concepts.

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Mastering Engineering Programming: Understanding Variables and Expressions

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  1. Engineering 1020 Introduction to Programming Peter King peter.king@mun.ca www.engr.mun.ca/~peter Winter 2010

  2. ENGI 1020: Fun with Vars • Lets look at some practical examples of using variables with functions • The following example has a function to calculate speed • In Class Example 4 • We can use variables in many ways • Cleaning up functions • Calling functions • Storing data

  3. ENGI 1020: Fun with vars • Which type should we use: • to count the number of students in a class. • to represent the slope of a roof. • to represent the response to a multiple choice exam question, the answer for which is a, b, c, d or e. • to represent the speed of a car. • to represent Avagadro's number (which if you don't know, you can Google).

  4. ENGI 1020: Fun with vars • When is a variable not a variable?

  5. ENGI 1020: Fun with vars • When is a variable not a variable? When it's a constant

  6. ENGI 1020: Fun with vars • Constants have many uses • Many engineering problems use big numbers that don't change • pi = 3.14159265 • e = 2.71828183 • g = 9.80665 m/s • We want these numbers in memory so we can use them • BUT! They shouldn't change

  7. ENGI 1020: Fun with vars • C++ allows us to create a non-variable variable const float PI = 3.14159265 • The const is a special keyword that tells the compiler to create a variable as before • Name, address, type, value • … but keep it locked so that nobody can change it • For style we put their names in capitals

  8. ENGI 1020: Expressions • What is an expression? • A combination of variables, constants, operators and functions which is progressively evaluated an operation at a time until it is reduced to a final value. • No matter what's included, an expression will be progressively reduced (evaluated) to a single value!

  9. ENGI 1020: Expressions • Arithmetic expressions • Two flavours: • Integer • Floating point (real) • The computer handles each in a very different manner • Integer operations are much faster (in computer time) • The floating point operations tend to be more powerful and useful

  10. ENGI 1020: Expressions • Operators • Two types • Unary – only have one operand • Binary – two operands • For Integers • Unary operators are: +, - • Binary operators are: +, -, *, / % • For real numbers • Unary operators are: +, - • Binary operators are: +, - *, /

  11. ENGI 1020: Expressions • Integer operators • Take integer operands and return an integer • Don't round • 11/7 would return 1 • Real operators • Take real operands and return a real

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