CSCI 235 — diff C Java 2

Our reference

• Chapters 7 to 14 of An Introduction to the C Programming Language and Software Design

But let’s start with some Fall 2015 CSCI 255 notes on C vs Java.

Chapter 7 — Pointers

• Draw elements of the following types
  • int *
  • char *
  • int **
  • void *
• Two new operators
  • unary & — address-of
  • unary * — dererence
  • study examples on page 50
• Examples of assigned to pointers and pointers to pointers
• The const declaration modifies
  • const int* pA ;
  • int const* pB ;
• call by reference (vs call by value)
  • Write an integer swap routine
  • C++ reference
  • strtol man page — this is hard
• arrays are constant pointers
• the mysteries of pointer arithemetic
• passing a function with pointers
  • C qsort vs Java sort
• Spring 2017 CSCI 255 notes
• Problem 15 of Spring 2017 CSCI 255 final
• Fall 2011 ECE 209 notes

Chapter 8 — Arrays and Strings

• Size of array is usually set in declaration
  • until you get to Chapter 9
• What a hack to find the size — sizeof(P)/sizeof(*P)
• Strings are null terminated char arrays
• C string library
• arrays of pointers
• multidimensional array

Chapter 9 — Dynamic Memory

Concentrate on sections 9.1—9.3: We are skipping the CSCI 202 stuff.

• Memory regions of C
• malloc and friends
• There is no garbage collection in C: use free

Chapter 10 — The C Preprocessor

• Fall 2009 ECE 209 C Preprocessor notes
• Try: gcc -E pointers.c > pointers.c-after-cpp

Chapter 11 — Structures and Unions

• A C struct is a Java class with only public fields — no methods
• A C union is strange, but useful
  • /usr/include/netinet/ip.h vs IP4 header
  • /usr/include/netinet/ip_icmp.h vs ICMP header
• Fall 2011 ECE 209 structure notes (with linked lists)
• Fall 2011 ECE 209 union examples

Chapter 12 — Bitwise Operators

We did much of this in Chapter 2 of the textbook.

• Bitwise operators: Just like Java except there is no >>>
  • C’s signed >> is like Java’s >>
  • C’s unssigned >> is like Java’s >>>
• Bitwise logical operators have a lower precedence than relational operators: x & b == c is x & (b == c)
• Bit-fields are used in the IP and ICMP headers

Chapter 13 — Input and Output

• %[flags][width][.precision][length]specifier
  • The C/C++ printf is a bit like the Java format
• %[*][width][length]specifier
  • The C/C++ scanf is very different from the Java Scanner
  • C input uses pointers
• In practice C++ I/O, with its heavy use of operator overloading and multiple inheritance, does not look at all like C and Java I/O
• File control: fopen and fclose
• Stream access
  • Character: fgetc and fputc
  • String: fgets and fputs
  • Record: fread and fclose
• Random access: fseek and ftell
• Command line arguments
• Fall 2010 ECE 209 formatting notes

Chapter 14 — Generic Programming

This is not a strong point of C!

• typedef: frequently used by experienced programmers
• macros: be very careful
• union: be very careful
• void *: the generic pointer
• qsort(): learn how to use it

C I/O example from last term

• problem
• solved