Lesson 1: Introduction to Computation and Programming

Question 1

Algorithm

Answer 1

• An algorithm is a sequence of instructions for solving a particular type of problem.

…similar in meaning to: recipe, process, method, technique, procedure, routine.

Question 2

Computation Problems

Answer 2

• Given a value (or set of values) called inputs

- Produce some value (or set of values) called outputs

Question 3

Computation

Answer 3

• The transformation of data from inputs to outputs.

Question 4

Statement of a Computational Problem

Answer 4

• Specifies the inputs and desired outputs (including their types and any restrictions).

Example: Given two coordinates (in lat-lon), compute the great circle distance (in nm) between them.

Question 5

Instance of a Computational Problem

Answer 5

• Specifies the inputs and consists of all the inputs needed to compute a solution to the problem.

(satisfying whatever constraints might be imposed by the problem statement)

Example: What is the great circle distance (in nm) between (37° 37’ 8” N, 122° 22’ 29” W) and (41° 58’ 46” N, 87° 54’ 16” W)?

Question 6

Important Properties of Algorithms

Answer 6

• Finiteness: An algorithm must always terminate after a finite number of steps.
• Definiteness: Each step of the algorithm must be precisely defined so that the actions can be carried out rigorously and unambiguously.
• Input: An algorithm has zero or more inputs—quantities that must be given before the algorithm begins.
• Output: An algorithm produces one or more outputs—quantities that have a specified relation to the inputs.
• Feasibility: All of the operations to be performed in the algorithm must be sufficiently basic that they can, in principle, be done exactly and in a finite length of time by hand (i.e., using pencil and paper).

Question 7

Programming

Answer 7

• The act of implementing algorithms in a computer language to solve a problem.

Question 8

In order to be successful in programming, you need:

Answer 8

• A specification of the computational problem to be solved:
• – the inputs (their types, meanings, restrictions)
• – the outputs (their types, meanings, restrictions)
• An algorithm to solve the problem.
• – Is it correct?
• – Is it efficient (how many resources does it require)?
• A means for storing and manipulating program data:
• – variables (types)
• – data structures (complex organizations of variables)
• A language for specifying the instructions: this controls the flow of program execution.

Question 9

Computer

Answer 9

A machine that executes a set of instructions.

Question 10

Instructions can be implemented in electronic hardware:

Answer 10

• Advantage: fast execution

- Disadvantages: single purpose, can’t be changed

Question 11

Software

Answer 11

• Flexibility comes from the developement of software (logical instructions) that can be executed on standardized hardware (e.g., computer processing units or CPUs)

Question 12

Machine Code

Answer 12

• Instructions that can be executed directly by the computing machines.
• – specific to hardware
• – expressed in binary

Question 13

Computer Programming Language

Answer 13

• A higher level abstraction.
• – hardware independent
• – “human readable” instructions that make it more natural to implement an algorithm

Question 14

Debugging

Answer 14

• The systematic process of removing bugs from code to obtain the intended program behavior

Question 15

Domain Specific Programming Languages

Answer 15

• Languages dedicated to a particular problem domain, a particular problem representation technique, and/or a particular solution technique

Examples: Matlab, R, S-Plus, GAMS

Question 16

General Purpose Programming Languages

Answer 16

• Languages intended to be used in any context; do not rely on particular problem domains, represenations, or solution techniques
  Examples: Fortran, Pascal, C, C++, Java, Python, Ruby

Question 17

Program

Answer 17

• The (computer) code that implements that logic.

Question 18

The task of an analyst in using computation to solve problems:

Answer 18

1. Define the problem (statement of computational problem)
2. Identify (or design) the algorithm.
3. Implement the algorithm in computer code.
4. Manage the process (testing, debugging, documenting for yourself and others)