created 06/16/00

Programming Exercises


Exercise 1 — Play with a Hex Dump

Use Irfanview (or other hex dump program) to examine the contents of several text files and binary files.

When you examine a text file, the hex dump will show the bit patterns that represent the characters (using the ASCII scheme). The right side of the display will show the characters that are represented. For example, here is the display of a text file created with NotePad:

hex dump of a text file

It shows that the very first byte of the file contains the bit pattern 0x57 (which is 01010111) and that this pattern represents the character 'W' .

Bit patterns are represented using hexadecimal notation, where every four bits form a pattern and each pattern is given a name according to this scheme:

Name 01 2 3 4 5 6 7
Pattern00000001 0010 0011 0100 0101 0110 0111
Name 89 A B C D E F
Pattern10001001 1010 1011 1100 1101 1110 1111

 

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Exercise 2 — Counting Loop

Write a program that writes a file the values 0 to 64 using data type short. (Use writeShort()). Examine the file with a hex dump.

Now write a program that writes a file the values 0 to 64 using data type int. (Use writeInt()). Examine the file with a hex dump.

Now write a program that writes a file the values 0.0 to 64.0 using data type double. (Use writeDouble()). Examine the file with a hex dump.

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Exercise 3 — Data Translator

Write a program that asks the user for the name of an input text file. The text file (which could be created with NotePad) will contain integers in character format, one per line, such as follows.

12
1023
-56
84781
0
-9371

The program also asks for the name of an output file. The program then reads the input file line by line until end of file. Each input integer is translated into int data (use Integer.parseInt()) and written to the output file using DataOutputStream.writeInt().

Look at the input file and output file with the DOS command DIR and, if possible, with a hex dump program.


C:\Programs>java  IntCopy
Input file -->ints.txt
Output file -->ints.bin

C:\Programs>dir

06/16/00  04:33p                 1,881 IntCopy.class
06/16/00  04:33p                 1,920 IntCopy.java
06/16/00  04:35p                    24 ints.bin
06/16/00  04:35p                    30 ints.txt

Write the input loop so it catches NumberFormatExceptions and echos the offending line. Here is another input file:

0
1
2
3
4
Rats, this won't work
6
7
8

And the corresponding run of the program:

C:\Programs>dir
Input file -->oops.txt
Output file -->opps.bin
Poor input data:Rats, this won't work

C:\Programs>

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End of Exercises.