A Level Computing#BristolMet

Session Objectives#U2S11

MUST identify built-in string manipulation functions

SHOULD correctly use string manipulation functions

COULD combine string manipulation in a working program

Create a password strength indicator program

A Level Computing#BristolMet

Key Words

Built-in

LEFTLength

String Locate

MID

A Level Computing#BristolMet

String Manipulation - Extraction

Most languages have built-in functions to extract part of a string , often being called LEFT, RIGHT or MID

LEFT (<string>, <number of characters>) i.E LEFT (“Computing”, 3) returns “Com”

but MID (<string>, <starting position>, <number of characters>)

i.e (“Computing”, 4, 3) returns “put”

TASK:Experiment with the string extract functions using Python and then Javascript. Is the syntax and logic the same?

A Level Computing#BristolMet

String Manipulation – Length

Again, ,most languages have a function to calculate the number of characters in a particular string, usually:

LENGHTH (<string>) i.e LENGTH (<“Computing”>) returns 9

TASK: Try this in Python or Javascript.

It is particularly useful validate passwords and increase strengths based on the numbers of characters used.

EXT: Design, create and test a program that will encourage strong passwords to be used. What will you have to do first in order to write a suitable software solution?

A Level Computing#BristolMet

Password Program

Problem analysis:

The program MUST

• Take user input and store as string• Measure length of string• Make decision based on length whether Strong, Medium or

Weak• Output Decision

A Level Computing#BristolMet

String Manipulation - Locate

Another common in-built function is facilitate the ability to search a string for certain sequences of characters.

i.e LOCATE (<search string>, <main string> This varies between languages

LOACTE (“put”, “Computing”) would return 4 as it is found from the 4th character along in the string.

TASK: Attempt in Python or Javascript and test to see working by getting results of 0 and above.

TASK 2: Complete Questions 1-2 in the Activity on p.106

EXT: Create the program in Q3.