1. Differences between Java and C
Professor Hugh C. Lauer CS-2303, System Programming Concepts
(Slides include materials from The C Programming Language, 2nd edition, by Kernighan and Ritchie, Absolute C++, by Walter Savitch, The C++ Programming Language, Special Edition, by Bjarne Stroustrup, and from C: How to Program, 5th and 6th editions, by Deitel and Deitel)
CS-2303, A-Term 2012
Differences between Java and C

2. Differences between Java and C
Java is derived from C++, hence from C
Many of its syntactic characteristics are similar to C
However, there are some huge differences
CS-2303, A-Term 2012
Differences between Java and C

3. Differences between Java and C
Expressions
Arithmetic operators are the same:–
+, –, *, /, %, ++, – –
Numerical type conversion is mostly the same
Java spells out divide by zero, NaN (not a number, etc.)
C & C++ are machine dependent
Check the textbooks for details
CS-2303, A-Term 2012
Differences between Java and C

4. Differences between Java and C
Relational Operators
Relational operators work the same way but return different results:–
>, >=, <, <=, ==, !=
In Java, they return values FALSE and TRUE
C/C++ operators return values 0 and 1
In C/C++,
a value of zero means “false”
any value that is not zero means “true”
E.g., 1, 5, , , × 10-34
Very important!
CS-2303, A-Term 2012
Differences between Java and C

5. Conditional and Bitwise Operators
Conditional execution operators are same in Java and C/C++:–
||, &&, ? followed by :
Bitwise operators are same in Java and C/C++:–
|, &, ^ for bit-by-bit operations within a word
Shift operators differ a little bit
<< (left shift) is the same
>> (right shift) is machine dependent in C/C++
I.e., whether to fill from left with zeros or sign bits
CS-2303, A-Term 2012
Differences between Java and C

6. Assignment and Unary Operators
Assignment operators work the same:–
=, +=, –=, *=, /=, &=, |=, ^=
The following unary operators are available C/C++ but not in Java
~ invert the bits of a word
* pointer dereference
& pointer creation
(type) cast (i.e., forceable type conversion)
sizeof # of bytes in operand or data type
–> pointer dereference with field selection
CS-2303, A-Term 2012
Differences between Java and C

7. Summary about Expressions and Operators
Pretty much the same in C/C++ and Java
Be sure to check details in textbook
Be sure to check operator precedence
Table 2-1 in K&R (p. 53)
Figure 2.3 in Absolute C++
Note: Absolute C++ uses the term “Display” to mean “figure”
CS-2303, A-Term 2012
Differences between Java and C

8. Differences between Java and C
Statements
Statements in C/C++:–
Labeled statement
Expression statement
Compound statement
Selection statement
Iteration statement
Jump statement
CS-2303, A-Term 2012
Differences between Java and C

9. Differences between Java and C
Statements
Statements in C/C++:–
Labeled statement
Expression statement
Compound statement
Selection statement
Iteration statement
Jump statement
E.g., cases of a switch statement
Similar to Java
CS-2303, A-Term 2012
Differences between Java and C

10. Differences between Java and C
Statements
Statements in C/C++:–
Labeled statement
Expression statement
Compound statement
Selection statement
Iteration statement
Jump statement
Any expression followed by ';'
Much like to Java
CS-2303, A-Term 2012
Differences between Java and C

11. Differences between Java and C
Statements
Statements in C/C++:–
Labeled statement
Expression statement
Compound statement
Selection statement
Iteration statement
Jump statement
Sequence of statements enclosed in "{}"
Called a “block” in Java
CS-2303, A-Term 2012
Differences between Java and C

12. Differences between Java and C
Statements
Statements in C/C++:–
Labeled statement
Expression statement
Compound statement
Selection statement
Iteration statement
Jump statement
switch (expr) {cases}
if (expr)
statement
else
Same as in Java
CS-2303, A-Term 2012
Differences between Java and C

13. Differences between Java and C
Statements
Statements in C/C++:–
Labeled statement
Expression statement
Compound statement
Selection statement
Iteration statement
Jump statement
while (expr) statement
do statement while (expr);
for (exp1; exp2, exp3) statement
Very similar to Java
CS-2303, A-Term 2012
Differences between Java and C

14. Differences between Java and C
Statements
Statements in C/C++:–
Labeled statement
Expression statement
Compound statement
Selection statement
Iteration statement
Jump statement
break;
continue;
return expr;
Very similar to Java
goto
Not present in Java!
Not allowed in this course
CS-2303, A-Term 2012
Differences between Java and C

15. Summary about Statements
Pretty much the same in C/C++ and Java
Be sure to check details in textbooks and/or reference manuals
CS-2303, A-Term 2012
Differences between Java and C

16. Formatted Input & Output
Very different between C and Java
Very different between C and C++
Handled by library functions in C
printf()
scanf()
getc()
putc()
Many others!
CS-2303, A-Term 2012
Differences between Java and C

17. printf() – Print formatted data
printf("string containing '%' specifiers", expr1, expr2, expr3, …);
Copy the string, character-by-character, to the output stream
When the ith '%' is encountered, treat it as a conversion specifier for converting the value of expri
Copy the converted value to the output per instructions encoded in the conversion specifier
Return number of characters printed
CS-2303, A-Term 2012
Differences between Java and C

18. printf() conversion specifiers
K&R, pp 154 & 244
%d or %i
Treat expression as a decimal number (with sign) %u
Treat expression as unsigned decimal number %f
Treat expression as double precision floating point number; print without exponent
%e or %E
Treat expression as double precision floating point number; print with exponent (base 10) — scientific notation %c
Treat value of expression as the code for a single character %s
Treat expression as a pointer to a string
Later in this course
CS-2303, A-Term 2012
Differences between Java and C

19. printf() conversion specifiers (continued)
Conversion specifiers may optionally contain
Right or left alignment in the field
Minimum field width (padded on right or left)
Precision – i.e.,
Maximum length of string
Number of decimal places of floating point value
Size of data type
E.g., short, double, float, etc.
Examples
%6d – print signed decimal number in 6-char field
%8.4f – print 64-bit floating point number with four places after decimal point, field width of 8 characters
%hu – print an unsigned short integer (i.e., 16 bits in Pentium)
CS-2303, A-Term 2012
Differences between Java and C

20. scanf() — Scan formatted data
scanf("string containing '%' specifiers", &var1, &var2, &var3, …);
Scan the input, matching the string character by character
When the ith '%' is encountered, treat as a conversion specifier for converting next sequence of characters and storing result in vari
Copy the converted value to the output per instructions encoded in the conversion specifier
Stop if input does not match string OR if conversion was not successful
Return number of successful conversions
Note ampersands
CS-2303, A-Term 2012
Differences between Java and C

21. scanf() – Typical Usage
int j;
double x;
scanf("%d%f", &j, &x);
Scan the input, skipping blanks and tabs
Try to match a signed integer; if successful, store result in j and continue
Continue scanning, skipping blanks and tabs
Try to match a floating point number. If successful, store in x
Stop if unsuccessful or new-line encountered
Return number of items stored
CS-2303, A-Term 2012
Differences between Java and C

22. Differences between Java and C
scanf() Details
K&R Table B-2 (p. 246)
printf() and scanf() are both needed for Lab #1 and Programming Assignment #1
CS-2303, A-Term 2012
Differences between Java and C

23. Differences between Java and C
Summary
Differences and similarities between Java and C
Expressions
Statements
There are lots of other differences
Will be covered during the course
CS-2303, A-Term 2012
Differences between Java and C

24. Differences between Java and C
Questions?
Next Topic
CS-2303, A-Term 2012
Differences between Java and C