C Language Programming - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 258

Constants are often needed in forming a statement. There are four types of constants: inte-
gers, characters, floating-point numbers, and strings.
There are seven arithmetic operators : 1, 2, *, /, %, 11, and 22. There are six bitwise
operators : &, |, ^, ,, .., and ,,. Bitwise operators can be applied only to integers. Relational
operators are used in control statements. They are 55, !5, ., .5, ,, ,5, &&, ||, and !.
The control-flow statements specify the order in which computations are performed. Con-
trol-flow statements include if-else statements, multiway conditional statements, switch statements,
for-loop statements, while statements, and do-while statements.
Every C program consists of one or more functions. If a program consists of multiple func-
tions, their definitions cannot be embedded within another. The same function can be called
from several different places within a program. Generally, a function will process informa-
tion passed to it from the calling portion of the program and return a single value. Informa-
tion is passed to a function via special identifiers called arguments (also called parameters ) and
returned via the return statement. Some functions, however, accept information but do not
return anything (for example, the library function printf ).
A pointer holds the address of a variable. Pointers can be used to pass information back
and forth between a function and its reference (calling) point. In particular, pointers provide a
way to return multiple data items from a function via function arguments. Pointers also permit
references to other functions to be specified as arguments to a given function. Two operators are
related with pointers: * and &. The * operator returns the value of the variable pointed to by the
pointer. The & operator returns the address of a variable.
Data items that have common characteristics are placed in an array . An array may be one-
dimensional or multidimensional. The dimension of an array is specified by the number of
square bracket pairs [ ] following the array name. An array name can be used as an argument to
a function, thus permitting the entire array to be passed to the function. To pass an array to a
function, the array name must appear by itself, without brackets or subscripts. An alternative
way to pass arrays to a function is to use pointers.
A variable defined inside a function is an internal variable of that function. External vari-
ables are defined outside of any function and are thus potentially available to many functions.
The scope of a name is the part of the program within which the name can be used. The scope
of an external variable or a function lasts from the point at which it is declared to the end of the
file being compiled.
Tutorials for using the CodeWarrior IDE and ImageCraft ICC12 are provided at the end of
this chapter. The tutorial for using the EGNU IDE is in Appendix E. All three IDEs are window
driven, but only CodeWarrior provides source-level debugging capability.
Neither ImageCraft nor EGNU IDEs provides many library functions to the user. Three sets
of library functions are provided in the complementary CD and are listed in Table E.1 of Appen-
dix E. These three sets of library functions are stored in files stdio0.c, delay.c, and convert.c .
5.16 Exercises
E5.1 Assume that ax 5 83 and bx 5 11. What is the value of ax / bx ?
E5.2 Assume that ax 5 97 and bx 5 ax % 23. What is the value of bx ?
E5.3 Assume that ax 5 0x39 and bx 5 ax ^ 0x79. What is the value of bx ?
E5.4 Assume that ax 5 0x9D and bx 5 ax ,, 2. What is the value of bx ?
E5.5 Assume that ax 5 0x6B and bx 5 ax & 0xDE. What is the value of bx ?
E5.6 Write a C function to test whether an integer is a multiple of 8. If the number to be tested
is a multiple of 8, the function returns a 1 to the caller. Otherwise, it returns a 0 to the caller.