Example Program:
Invoice Processing
• Details of an invoice are available as follows:
The number of items on the invoice - n
For each item
an item code (6 digits), a quantity and
a unit cost (pounds,pence)
Thus a typical set of input values for an invoice might be:
3
161432 5 6 50
543289 10 2 25
876234 2 10 75
Example Program:
Invoice Processing
• indicating that there are three items on the invoice
• the first item having an item code of 161432, an order
quantity of 5 and a unit price of six pounds fifty pence.
• Assume that the days date will also be entered.
• Write a C++ program to enter details of such an invoice
and to output an invoice which indicates the total cost of
each item and the total cost of the invoice together with
full details.
• The above details might produce an invoice as follows:
Example Program:
Invoice Processing
Invoice date: 10/6/96
Item quantity unit price total price
161432 5 6.50 32.50
543289 10 2.25 22.50
876234 2 10.75 21.50
Total 76.50
Example Program:
Invoice Processing
• A first attempt at an algorithm might be:
initialise.
enter date.
enter number of items into n.
output headings.
for n items do
{
enter a record.
calculate total cost of item.
accumulate total invoice cost.
write line of invoice.
}
output total cost.
Example Program:
Invoice Processing
• Assume that there are four programmers
available to implement this program.
• There are four major operations inside the for
loop hence each programmer could be given
one operation to implement.
• The best way to do this is to use a function for
each operation.
• Each programmer can then be given a precise
definition of a function.
Example Program:
Invoice Processing
• For example consider the operation enter a
record.
• This function must read in the integer quantities
item number, quantity and unit price in pounds
and pence.
• Hence it has no input parameters and four
output parameters.
• A definition of the function could then be written
as follows:
Example Program:
Invoice Processing
Function name: dataentry
Operation: Enter a record
Description: Enters four integers from the current
input line and returns their values.
Parameters: Output parameter int itemno
Output parameter int quantity
Output parameter int unitpounds
Output parameter int unitpence
Example Program:
Invoice Processing
Function name : calccost
Operation : Calculates the cost for a single item.
Description : Given the unit price of an item in
pounds and pence and the quantity of
the item calculates the total cost in
pounds and pence.
Parameters : Input parameter int quantity
input parameter int unitpounds
input parameter int unitpence
output parameter int totalpound
output parameter int totalpence
Example Program:
Invoice Processing
Function name : acctotal
Operation : Accumulates the total cost of invoice
Description : Given current total invoice cost and
the total cost of an invoice item
calculates the new total invoice cost.
Parameters : input parameter int totalpound
input parameter int totalpence
input & output parameter int invpound
input & output parameter int invpence
Example Program:
Invoice Processing
Function name : writeline
Operation : Writes a line of the invoice.
Description : Given the item reference number, the
quantity, the unit price and total
price of an item outputs a line of
the invoice.
Parameters : input parameter int itemno
input parameter int quantity
input parameter int unitpounds
input parameter int unitpence
input parameter int totalpound
input parameter int totalpence