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unit 2.2 programming
- A memory location where information
relevant to the program is called: 'a variable'
if it changes throughout the program or, 'a
constant' if it is fixed for the duration of the
program
- Variables are
from which we
build up our
programs:
whole
numbers, real
numbers,
string, boolean
- RAM is divided in
memory locations with
long hexadecimal
- Constants: are values that
don't change as the
program runs
- Analogy with spreadsheets : a
grid of memory
locations(cells) can hold
values . Each cell has an
address/label and holds a
value or a reference to
another address
- Computers are general
purpose problem solving
machines, they need: raw
materials(inputs), time
and instructions to
process the inputs, the
results(outputs)
- Variable: memory
location with a
descriptive label
- Operators: represent
the operations that are
performed on the data
+ - / * ^
- Pseudocode for
string operations:
convert a string to
UPPERCASE.
convert a string to
lowercase. length
of a string.
substring
- ARITHMETIC OPERATORS: + Addition
- Subtracion * Multiplication /
Division MOD modulus DIV Quotient
^ Exponentiation
- COMPARISON OPERATORS: == equal to != not equal to < less than <=less
than or equal to > greater than >= greater or equal to
- Benefits of sequencing: each line follows
the next. Create simple programs very
quickly. Easy to follow for a small
program. Fundamental principal of a
program- start at the top and finish at
the bottom
- Disadvantages of sequencing:
not at all efficient. Becomes very
difficult to follow with large
programs. Extremely hard to
maintain.
- Text files are used to store a
variety of data: lists of names, logs
of events, tables of data
- String handling: to get the length
of the string, to get a substring,
the string will start with the 0th
character, ascii conversion
- Tabulation- the process of writing data
to a table is known as tabulation
- SQL- Standard
Query
Language
- Nested select refers to
multi-stage
filtering.Limitations of the
nested select: no sorting
allowed. must be in ( ). can
only return one column
usually. should only return
one row
- Array is an ordered
collection of related
data where each
element is accessible
by a number(index)
- Sub programs can be
used to save time and
simplify code. The
main types of sub
programs are
procedures and
functions.
- Procedure: are sets of
instructions stored under
one name
- Functions: are similar to
procedures but always
return a value to the
main program.
- Variables and constants both
run data. Variables will always
return a value and can be
changed whereas constants
bring back a value but cannot
be changed.
- Two
programming
constructs are
selection and
sequence.
- Integers are whole
numbers. String are
text. Boolean is
true/false. Real data
can be numbers with
decimals.
- Casting is when
the values for a
variable can be
interpreted.
- Database
record is a
data for an
entity in a set
of database.
- SQL- Select, From, Where
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