Unit 6 Software & Development
Assignment 2
Max Wade
P3 – explain sequence, selection and iteration as used in computer programming
P4 – outline the benefits of having a variety of data types available to the programmer
Task
In your role of Development Consultant at SNC PLC, your line manager Jane Fletcher
has asked you to expand the information contained in the wiki you made for her
previously to include some additional data.
1. Taking the data types outlined on page 3 of this document, for each give an
explanation of what each type may be used for, and what data can be validly
contained within a variable for each type. (Background for P4)
Text; integer; floating point; byte; date; Boolean; other eg char, smallint
When making a program there are many different data types that are used for
different types of data. Some of the main data types are String, Integer, Floating
point, byte, date, Boolean and others are char and smallint. For each of these
examples I will be telling you what they are used for and which types of data can be
validly contained within them.
The data type String will normally be a sequence of characters that either literal
constant or as some kind of variable. So sequences of unsigned 16-bit code points
from the value 0 to 65525 can be held in this data type.
Integer, this data type will be able to hold 32-bit signed integers which range from
the values -2,147,483,648 to 2, 147,483,647. It is a data type that provides an
optimal performance on a 32-bit processor. The default value of integer is a 0.
Floating Point has data types, single and double. The single type will need 4 bytes of
memory; it is able to store negative and positive values between. The negative
values are will be between -3.402823 x 1038 and -1.401298 x 10-45 and the positive
values are between 1.401298 x 10-45 and 3.402823 x 1038.
The double data type needs a bigger memory of 8 bytes but can store much more
values in the positive and negative values.
The data type byte is used for containing binary data; binary data is typically data
that could contain null bytes. This data type variables are stored in unsigned 8-bit
(1-byte) numbers that can be 0 to 255.
Date data types are stored as 64 but integers that represent dates ranging from
January 1 of the year to December 31 of the year. Date values must be within the
format M/D/YYYY.
Unit 6 Software & Development
Assignment 2
Max Wade
The Boolean data type is stored as 16-bit numbers, but they must be true or false.
Boolean values can be compared to test for equality or inequality. You can also use
Boolean column to store what a Boolean expressions returns.
The other data types are char and Smallint. Char data type is stored as 2-bytes
numbers in value from 0 to 6555. Each of the numbers represents a single Unicode
character. Smallint data type is a data type that is stores small whole numbers that
range from -32,767 to 32,767.
2. With the information from point 1 above, explain the benefits to the
programmer of having different data types available. (P4)
By a programming having different data types available for programmers to use they
will have many benefits when having to add data it their program e.g. it will allow
for less waste when storing data, without having to re-implement standard data
types you can write your application code and will enable code parameters to be
more expressive.
Another one of the main reasons to why there are different data types is that each
bit of data is aligned with the data type which has specifically the amount of memory
it can be stored with, so it is more efficient with memory. Also data that have their
own data is easier to secure as it is easier to tell when a pointer to block memory
with data had be compromised, this is because by have specific data types for pieces
data with exact limits for what data can be stored.
Data types will make the data less likely to make mistakes as the data types of
behaviour are closely matched. Another advantage to having different data types is
that because more errors are caught before it is put into binary code where they are
harder to track down. They cause more errors before they are converted because
specific types will be in small number of places in the programmer’s code.
3. Explain the different control structures that are available within a
programming environment (sequence, selection and iteration). You may give
examples if it helps to make your explanation clearer. (P3)
One of the most important parts of programming is being about to control the
execution of a program, so that lines of code are being executed at the right
moments, or that some bits of code are being repeated. When you are within a
programming environment it is important that you know what the different control
structures are and what they do. I will explain the three main categories, Sequence,
Selection and iteration, to help with pointing out the differences between.
So the first control structure that I will explain is Sequences. Sequences in terms of
within a programming environment are the order of execution. It will normally be in
reference to the order of which the code will be executed. The code will be done line
Unit 6 Software & Development
Assignment 2
Max Wade
by line. Most lines of code use this it is very boring, it is just following a given
sequence, doing one instruction after the other.
Selection is the method of control to the execution of a sequence. Large blocks can
be created by using statements testing a condition, or to switch statements
evaluating a variable. This is done to control and change execution of programs
depending on the environment and changing variables. So it basically where you
select between two or more flows.
Iteration normally is used for referring to collections and arrays of data. It means to
visit each item in a particular collection, each item can only be visited once, and they
can either be order or in an irregular order. For example this being in an order just
simply counting up from 1-5, you are iterating the first 5 numbers.
It can also be known for repetition, for some codes they can be executed many
times or not at all. They can be executed to a fixed number of times or indefinitely
for it to reach a condition.