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CPSC 427: Object-Oriented Programming Handout #4

Problem Set 2

This short assignment is designed to deepen your understanding of C++ I/O and of character
representations.
1 Assignment Goals
1. Learn how to use command line arguments.
2. Learn how to open a file and read its contents.
3. Learn how characters are represented by bytes in the computer.
4. Learn the difference between a character and its ASCII code.
5. Learn how to obtain the ASCII code of a character stored in a variable of type char.
6. Learn how to print the character whose ASCII code is stored in a variable of type int.
7. Learn how to print an int as a decimal number.
8. Learn how to print an int as a hex number.
9. Learn how to test if a char is printable.
10. Learn how to use the output manipulators dec, hex, setw(), and setfill() to control
the printed form of numbers.
11. Learn precisely what inval does to the istream in when val has type int.
12. Learn how to use in.get(ch) to read a single character from in.
13. Learn precisely what out<<val does to the ostream out when val has type int and when
val has type char.
14. Learn how to recover after a failed attempt to read a decimal number from an istream.
2 Problem
You should review Lecture 4, which gives an overview of C++ I/O. You should also look at the material on C++ I/O in the two textbooks, Applied C and C++, Chapter 14 and Exploring C++, Chapter
3 to you make sure you understand I/O in enough depth to do this assignment. You can find details
on the individual functions and manipulators in http://www.cplusplus.com/reference/iostream/ for.
You should write a program that takes the name of a file as a command line argument. The file
will consist of a mixture of letters, digits, punctuation, whitespace characters, and control characters.
Your program should open the file on an input stream in and declare an int variable x. It should
then repeatedly attempt inx. If a number is successfully read into x, then x should be printed in
decimal on a line by itself.
If the attempt to read x fails, then the next character should be read from the stream using
in.get(ch), where ch has type char, and a one-line “Skipping. . . ” message should be printed.
Depending on the character read, the message might look like either of the following:
Skipping char: 116 0x74 ’t’
Skipping char: 0 0x00
2 Problem Set 2
In each case, the ASCII code of ch is printed first in decimal, right-justified in a 3-character field
without zero-fill, and then again in hex, prefixed by “0x”, followed by a right-justified 0-filled hex
number in a 2-character field. If ch is printable as defined by isprint()1
, then it should also be
printed as a character, enclosed in single quotes as shown.
For example, if file data.in contains the text:
Score was 35to21.
the output should be:
—————————————————————
Ima Goetting Closeau
CPSC 427/527
Tue Oct 4 2016 11:18:06
—————————————————————
Skipping char: 83 0x53 ’S’
Skipping char: 99 0x63 ’c’
Skipping char: 111 0x6f ’o’
Skipping char: 114 0x72 ’r’
Skipping char: 101 0x65 ’e’
Skipping char: 119 0x77 ’w’
Skipping char: 97 0x61 ’a’
Skipping char: 115 0x73 ’s’
35
Skipping char: 116 0x74 ’t’
Skipping char: 111 0x6f ’o’
21
Skipping char: 46 0x2e ’.’
Loop exit
—————————————————————
Normal termination.
Be sure you understand why there is no “Skipping” line for the spaces following “Score” and “was”.
What happened to those characters?
3 Programming Notes
This program is very short and may be put entirely in the run() function in main.cpp.
You must read x using the stream extract operator . You may not use stringstream or
getline() or other methods to read the line as a string or to read individual digits that comprise
a decimal number. You must let the stream do your decimal to binary conversion. Do not call
atoi() or strtol() or any other means of manually converting a string to an int.
To obtain the ASCII code of a character stored in a char variable ch, cast ch to an int.
Similarly, to print a character whose ASCII code is stored in an int variable x, cast x to a char
before printing.
1
See http://www.cplusplus.com/reference/cctype/isprint/.
Handout #4—September 16, 2018 3
Grading Rubric
Your assignment will be graded according to the scale given in Figure 1 (see below).
# Pts. Item
1. 1 All relevant standards from PS1 are followed regarding submission, identification of authorship on all files, and so forth.
2. 1 A well-formed Makefile or makefile is submitted that specifies compiler
options -O1 -g -Wall -std=c++17.
3. 1 Running make successfully compiles and links the project and results in an
executable file readint.
4. 1 Your program gives a usage comment and terminates if the wrong number of
command line arguments are given. It gives a descriptive error comment if the
specified input file does not open.
5. 4 All instructions given in sections 2 and 3 are carefully followed.
6. 4 Your program correctly extracts all of the integers in the file.
7. 4 Your program prints a correct “Skipping. . . ” message following each failed
attempt to read an integer.
8. 2 The “Skipping. . . ” message exactly follows the examples and instructions, including spacing and when to print leading 0’s and when not to.
9. 2 Your program correctly handles end-of-file, regardless of whether the EOF is
immediately preceded by whitespace, a digit, or another character.
20 Total points.
Figure 1: Grading rubric.

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