Software Development Flashcards
Coding:
how alphanumeric data and control characters are represented by sequences of bits
American Standard Code for Information Interchange (ASCII)
- 7-bit code permitting (2)^7 = 128 different combinations
- commonly used in desktop computers
Extended Binary Coded Decimal Interchange Code (EBCDIC)
- used in IBM mainframe computers
- 8-bit code permitting (2)^8 =256 different characters
program
sequence of computer instructions that perform some function
- designed to implement an algorithm
algorithm
procedure consisting of a finite set of well-defined steps
source code statements:
- instructions like READ, GOTO, OPEN
- translated into machine-readable object code to produce executable program
variable
- used by a program to store a value
- can be known or unknown
declaration
- defines a variable
- specifies the type of data a variable can contain
- reserves space for the variable in the program’s memory
assignment
give values to variable
command:
instructs the program to take specific action
function:
specific operation grouped into a unit that can be called within the program
flowchart
- step by step representation of a specific procedure or algorithm
- -> terminal: begins and ends flowchart (pill shaped)
- -> input/output: defines an i/o operation (rhombus)
- -> processing: defines a calculation or data manipulation (rectangle)
- -> predefined process (subroutine): refers to a calculation or data manipulation formally defined elsewhere (square with stripes on left and right sides)
- -> decision: indicates a branch or question in the process flow (typically two options, such as yes and no) (diamond)
- -> connector: indicates flowchart continues elsewhere (circle)
- -> off-page: indicates flowchart continues on following page (looks like home base plate)
- -> annotation: indicates a comment (rectangle with dotted line)
machine language instructions:
- compatible with and readily understood by the central processing unit (CPU)
- each instruction must be expressed as a series of bits (intrinsic machine code)
- may be written in octal or hexadecimal for convenience, then converted to binary
- instructions consists of op-codes and operands
- -> op code : operation to be performed
- -> operand: storage location
assembly language
- next-higher -level language above machine language
- mnemonic codes specify operations
- operands referred to by variable name rather than address
macros
- blocks of code repeated verbatim at multiple locations in a program
- written once and the referred to by a symbolic name
assembler
- translates assembly language into machine language
linker
- combines portions of other programs or function libraries after assembly
loader
places the program in the computer’s memory in order to run it
A portion of computer code contains the instructions LR, SC and JL. Most likely these are A) machine language B) assembly language C) object code D) interpreted code
B) assembly language
–> assembly language usually consists of short commands such as LR for loading a value into the register, SC for storing a result in location C, and JL for jumping if the result is less than a given number. Assembly language is translated into binary machine language (also known as “object code”) by an interpreter or compiler program
relative computational speed languages
slower faster
<——————————————————————————————————————————————————————————–>
interpreted program pseudo-compiled compiled assembly language
structure:
in a structural language, each subroutine and other procedure has one specific entry point and one specific return point.
strong data typing
- different types of data are defined and cannot be interchanged
- for example, integers and real number cannot be combined in arithmetic statements
weak data typing
- data of one type can be used where data of another type is expected
- for example, the number 3 can be added to the alphanumerical string “4” to get 7. (in a strongly typed language, this would probably result in an error.)
portability
a portable language can be implemented on different machines
structured programming
- divides a procedure or algorithm into parts:
- -> subprograms
- -> subroutines
- -> modules
- -> blocks
- -> procedures
Recursive calls
- permits a subprogram to call itself
- requires less code, but uses more memory
order of operations
- calculations are performed in a specific order
- instructions in parentheses are done first
- symbols for mathematical operations
+ add
- subtract
* multiply
/ divide
X^B may be expressed as either:
X**B
X^B
Two floating point numbers, A and B are passed to recursive subroutine. If A is greater than or equal to 7, the subroutine returns the value of A. if A is greater than or equal to 7, the subroutine returns the vale of A. If A is less than the smaller of 7 and B, the subroutine divides A by 2, then passes the values of A and B to itself. Most likely what condition might this subroutine encounter?
A) overflow B) miscompare) C) infinite loop D) type mismatch
C) infinite loop:
Consider the case where A = 6 and B=9. 6 is not greater than or equal to 7, so control is note returned to the main program. 6 is less than the smaller of 7 and 9, so 6 is divided by 2, giving 3. The subroutine passes A=3 and = 9 to itself.
3 is not greater than or equal to 7, so control is not returned to the main program. 3 is less than the smaller of 7 and 9, so is 3 divided by 2, giving 1.5 The subroutine passes A=1.5 and B=9 to itself. the process repeat indefinitely because A will never be greater than 7
IF - THEN statement
IF < condition > THEN < action >
- fi the condition is satisfied, then the action is executed.
- If the condition is not satisfied, then the action is not executed and the program moves to the next operation
IF- THEN- ELSE statement
IF THEN ELSE
- If the condition is satsified, then action 1 is executed
- IF the condition is not satisfied, then action 2 is executed
DO WHILE loop
the set of instructions after the DO WHILE instruction and before the ENDWHILE instruction is repeated as long as the condition remains true.
DO WHILE loop
The set of instructions after the DO UNTIL instruction and the ENDUNTIL instruction is repeated as long as the condition remains false
FOR loop
- The set of instructions after the FOR instructions and before the NEXT instruction is repeated
- the counter range determines the number of loops
GOTO
- moves the program to an instruction elsewhere in the program
- avoided in structured programming
A structure computer program contains the following program segment.
Set G= 1 and X=0 DO WHILE G ≤ 5 G = G * X + 1 X = G ENDWHILE
What is the value of G after the segment is executed? A) 5 B) 26 C) 63 D) the loop never ends
B) 26
the first execution of the WHILE loop results in
G= (1) (0) + 1 = 1
X=1
the second execution of the WHILE loop results in
G= (1) (1) + 1 =2
X =2
The 3rd execution of the WHILE loop results in
G= (2) (2) + 1 = 5
X = 5
The WHILE condition is still satisfied, so the instruction is executed a fourth time
G= (5) (5) + 1 =26
X = 26
modular programming
- builds efficient larger applications from smaller parts ( modules )
object- oriented programming ( OOP)
- uses modular programming
- deals with objects, which are data structures (databases) and their associated functionalities
- exhibits characteristics like class, inheritance, data hiding, data abstraction, polymorphism, encapsulation, interference, and package
examples: Java, C ++, Python
Hierarchy of Operations
- operations within parentheses
- -> innermost pair first working outwards - exponentiation
- -> right to left - multiplication and division
- -> left to right - addition and subtraction
- -> left to right
Simulator
computer program that replicates a real-world system
digital model
- used in simulations, incorporating variables representing physical characteristics and properties of simulated system
- used to gain understanding of system’s characteristics and dynamics
- can be used to test multiple design scenarios
record
- collection of fields
- for example, a personnel record containing the fields name, age, and address
file
storage for groups of records
sequential file structure
- contains consecutive records and is read starting from beginning
- typical of data on magnetic tape
