Learn Programming with Livecoding.tv http://goo.gl/tIgO1I

Objectives  After viewing this presentation, the learner will be able to…  Given a task, create pseudocode  Given pseudocode, create a flowchart  Define/describe these terms: program, compile vs. interpret, loop, variable, function, syntax, code, debug, IF THEN ELSE

What is programming?  Series of instructions to a computer to accomplish a task  Instructions must be written in a way the computer can understand  Programming languages are used to write programs

What is programming?  Once the code (language) of a program has been written, it must be executed (run, started).  You may need to type the name of the program to start it, or use a word like RUN and the name of the program (in the old days, anyway).

What is programming?  Some programming languages (like Java or C++) require the code to be compiled (translated to binary) before it can be started.  Others (like JavaScript) are interpreted, meaning that each command is translated separately when the program is started.

What is a programming language?  Set of commands that a computer has been “taught” to understand  Languages that look like “machine code” (e.g., 82A8: jsr r5,@#82AE 82AC: sob r0,8296) are used for…  Writing games  Writing application programs (like Excel)  Other languages look like English (“high level,” e.g., PRINT “HELLO”)  Logo  JavaScript  And many more

What does programming look like?  Here are some examples of an instruction to print the word HI  Logo PR [HI]  JavaScript alert(“HI”);  FORTRANPRINT “HI”  BASIC PRINT “HI”  COBOL DISPLAY ‘HI’.  C++ printf(“HI”);  Pascal WRITELN(‘HI’);  Assembly XPRNT MESSAGE1 Language MESSAGE1 DC ‘HI’

How do you write a program?  Decide what steps are needed to complete the task  Write the steps in pseudocode (written in English) or as a flowchart (graphic symbols)  Translate into the programming language  Try out the program and “debug” it (fix if necessary)

What is pseudocode?  List of steps written in English  Like the instructions for a recipe  Must be in the right sequence  Imagine saying “bake the cake” and then “mix it up”

Sample Pseudocode  Task: add two numbers  Pseudocode:  Start  Get two numbers  Add them  Print the answer  End

What does a flowchart look like?  The pseudocode from the previous slide would look like this as a flowchart: Start Get 2 numbers Add them Print answer End

What are those funny symbols?  START/END  INPUT/OUTPUT  PROCESS  DECISION

What are those funny symbols?  START/END  Used at the beginning and end of each flowchart.

What are those funny symbols?  INPUT/OUTPUT  Shows when information/data comes into a program or is printed out. What are those funny symbols?

What are those funny symbols?  PROCESS  Used to show calculations, storing of data in variables, and other “processes” that take place within a program. What are those funny symbols?

What are those funny symbols?  DECISION  Used to show that the program must decide whether something (usually a comparison between numbers) is true or false. YES and NO (or T/F) branches are usually shown. What are those funny symbols? Y N X>7?

Another Sample: Calculating Age  Pseudocode:  Start  Get year born  Calculate age  Print age  If age > 50 print OLD  End

Another Sample: Calculating Age  Flowchart  Start  Get year born  Calculate age  Print age  If age > 50 print OLD  End Get yr Calc age Print age Age>50?OLD Y N Start End

Elements of a Program  All programming languages have certain features in common. For example:  Variables  Commands/Syntax (the way commands are structured)  Loops  Decisions  Functions  Each programming language has a different set of rules about these features.

Variables  Variables are part of almost every program.  A variable is a “place to put data” and is usually represented by a letter or a word. (Think of a variable as a Tupperware container with a label on it.)  Variable names cannot contain spaces.  Some programming languages have very specific limits on variable names.

Variables  Usually there are several ways to put information into a variable.  The most common way is to use the equal sign (=).  X = Y + 7 means take the value of Y, add 7, and put it into X.  COUNT=COUNT + 2 means take the current value of COUNT, add 2 to it, and make it the new value of COUNT.

Variables  Sometimes you must specify the type of data that will be placed in a variable.  Here are some examples of data types:  Numeric (numbers of all kinds)  String (text, “strings of letters”)  Integer (whole numbers)  Long (large numbers)  Boolean (true/false)

Variables  Variables may be classified as global or local.  A global variable is one that can be shared by all parts of a program, including any functions or sub-programs.  A local variable is one that is used only within a certain part of the program, for example, only in one function or sub-program.

Commands/Syntax  Programming languages are truly languages.  They have rules about grammar, spelling, punctuation, etc.  You need to learn the rules of a programming language, just as you learned to speak and write English.

Loops  A loop is a repetition of all or part of the commands in a program.  A loop often has a counter (a variable) and continues to repeat a specified number of times.  A loop may also continue until a certain condition is met (e.g., until the end of a file or until a number reaches a set limit)

Decisions  You saw a flowchart symbol for decisions.  A program often needs to decide whether something is true or false in order to see which way to continue.  Programs often use IF (or IF THEN or IF THEN ELSE) statements to show a decision.

Decisions  An IF statement always has a condition to check, often a comparison between a variable and a number.  The IF statement also must specify what to do if the condition/comparison is true.  These instructions (for “true”) may come after the word THEN, or they may simply be listed.

Decisions  In an IF THEN statement, when the condition is false, the program simply ignores the THEN commands and continues to the next line.  In an IF THEN ELSE statement, commands are given for both the true and false conditions.

Functions  In most programming languages, small sub-programs are used to perform some of the tasks.  These may be called functions, subroutines, handlers, or other such terms.  Functions often have names (e.g., getName or CALCTAX).

Functions  A function generally gets information from the main program, performs some task, and returns information back to the program.  Functions follow the same rules of syntax, etc. as the main program.  JavaScript code is primarily made of a series of functions.

Hints for Writing Code  “Code” means writing the program in the appropriate language  Be sure the code is exact (spelling, capitals/lower case, punctuation, etc).  Write part of the code, try it, then write more.

Debugging  To “debug” means to try a program, then fix any mistakes.  Virtually no program works the first time you run it. There are just too many places to make errors.  When you are debugging a program, look for spelling and punctuation errors.  Fix one error at a time, then try the program again.

Self-Check  A computer program is…  A series of instructions to accomplish something  A TV show  Written in Egyptian hieroglyphics  Can be written any way you want to

Self-Check  To “compile” a program means to…  Translate it into English  Translate it into binary code  Pile up the punch cards used for the program  Run the program as it was written

Self-Check  Pseudocode is…  The program as it is written in a programming language  The results of a program that makes secret codes  The logic of a program written in English  The logic of a program shown in a chart

Self-Check  The flowchart symbol to perform a calculation is…

Self-Check  The flowchart symbol to show a decision is…

Self-Check  Look at the flowchart section below. If the variable X is 5, what will print (K or 1st)? X > 5? YN Print “1st”Print “K”

Self-Check  Look at the flowchart section below. If the variable X is 5, what will print (K or 1st)? X > 5? YN Print “1st”Print “K” K will be printed. The answer to the question “Is X greater than 5?” is NO, since X is equal to (not greater than) 5.

Self-Check  Choose the correct flowchart symbol for each of these statements.  AGE>65?  Calc. Tax  START  Print NAME

Self-Check  A function in a program is… Something from trigonometry, like COSINE A sub-program, usually performing one task A way to check the accuracy of a program (a “function check”)

Self-Check  A variable in a program is… A letter or word that represents a place to store data A decision made within a program A small sub-program used to find errors

Challenge  Try to write pseudocode and create a flowchart for a program that calculates the average of three grades and prints the average.  The word GOOD should be printed only if the average is more than 80.

Challenge  Possible pseudocode  Start  Get three grades  Average them  Print Average  Average>80?  If Yes, print GOOD  End

Challenge  Possible flowchart  Start  Get three grades  Average them  Print Average  Average>80?  If Yes, print GOOD  End START END Get 3 grades Calc avg Print avg Avg>80?GOOD Y N

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