CS 1321 (Principles of Algorithm Design II):
Homework #1

Assigned:

January 14, 2000

Due:

January 21, 2000, at the beginning of class

Credit:

20 points.

Overview

    salesTax salesTaxRates TX 3.45 3.45 123.45

• salesTax is the name of the executable program.
• salesTaxRates is the name of a file with each line containing a two-letter state abbreviation, e.g., TX and CA, and the state sales tax rate written as a percentage, e.g., 6.25 for Texas and 7.25 for California. Sales tax rates are stored in a file because they continually change.
• TX indicates the state for which the sales tax should be computed.
• 3.45 3.45 123.45 indicates the item prices, written as decimal numbers with two digits after the decimal point.

    (3.45 + 3.45 + 123.45)*6.25% = 8.146875,

Details

• Use command-line arguments. Command-line arguments are yet another way for programs to obtain input from the user. When running many programs we wrote in CS1320, we prompted the user for necessary input such as filenames. Instead, any input known when the program begins can be sent to the program using command-line arguments.

  The example given above has six command-line arguments, separated by whitespace. Just as for arrays, they are numbered starting with zero. For example, argv[2] is TX, and argv[5] is 123.45.

  Here are the three rules for using command-line arguments:

  1. The main function should have two parameters: int main(int argc, char *argv[])
  2. To access the i-th argument, use argv[i].
  3. argv[argc] equals 0.
  The first parameter argc indicates the number of command-line arguments. The second parameter can be interpreted as an array ([]) of C-style strings, i.e., strings ending with a null-termination character. For example, argv[0] is a C-style string listing the executable program's name -- "salesTax" in the example given above.

  For an example of a program that uses command-line arguments, see echo1perline.cc.

  All command-line arguments are C-style strings, even for numeric arguments; e.g., argv[3] is the string ``3.45''. Tip: Use the strtod() library function to convert from a string to a double. Under Linux/Unix, you can get online help about this function by typing man strtod or info strtod. For example, use

  	strtod(argv[3], static_cast<char **>(0))
  	

  to convert the string to its double value 3.45. Be sure to include stdlib.h.

• Round fractions of pennies to the nearest penny. Round half-pennies up. For example, 10.5 cents is rounded to 11 cents, but 10.49999 cents is rounded down to 10 cents.

• Be sure your program works for any number of item prices and for a file of sales tax rates of any length. Be sure your program checks for enough command-line arguments and works even if the desired state is not found in the sales tax file.

• Remember to include comments in your program! At a minimum, include header comments giving your name and describing what the program does. See the tips on comments in guidelines for programming assignments.

What to turn in

• Use a subject header of "cs1321 homework 1".
• Submit a single file containing your C++ source code.