PICC LITE VARIABLE TYPES
The PICC Lite compiler supports the following basic data types:
• bit
• unsigned char
• signed char
• unsigned int
• signed int
• long
• unsigned long
• float
• double
Bit
A bit can store a Boolean variable (a 0 or a 1). Bit variables are usually used as flags in programs. In the following example, the variable answer can only take the values 0 or 1:
bit answer;
Unsigned Char
An unsigned char is 8 bits wide and can store a single ASCII character or an integer number in the range 0 to 255 (bit pattern ‘11111111’). In the following example, variables count and initial are declared as unsigned char and count is assigned a decimal value 120, and initial is assigned the ASCII character ‘T’:
Signed Char
A signed char (or simply char) is 8 bits wide and is used to store signed decimal numbers in the range –128 (bit pattern ‘10000000’) to +127 (bit pattern ‘01111111’). In the following example, the variable first is assigned the decimal value −180, and the variable count is
assigned a decimal value 25:
Unsigned Int
An unsigned int is 16 bits wide and can be used to store decimal numbers in the range 0 to +65 535 (bit pattern ‘1111111111111111’). In the following example, the variable result is
assigned the decimal value 28 512:
Signed Int
A signed int (or simply int) is 16 bits wide and it is used to store signed numbers in the range
−32 768 (bit pattern ‘1000000000000000’) to +32 767 (bit pattern ‘0111111111111111’). In the following example, the variable count is declared as a signed int and the negative value
− 25 000 is assigned to it:
Long
A long data type is 32 bits wide and is used to store large signed integer numbers. The range of numbers that can be stored in a long are −2 147 483 648 to +2 147 483 647. In the following example, the variable sum stores the integer value 45 000:
Unsigned Long
An unsigned long data type is 32 bits wide and is used to store large unsigned integer numbers. Numbers in the range 0 to 4 294 967 295 can be stored in an unsigned long data type. In the following example, the large number 3 200 000 is stored in the variable cnt:
Float
A float data type is 24 bits wide and is used to store noninteger fractional numbers (i.e. floating- point real numbers). Variables of this type are implemented using the IEEE 754 truncated 24-bit format. In this format a number consists of:
• a 1-bit sign bit;
• an 8-bit exponent which is stored as excess 127 (i.e. an exponent of 0 is stored as 127);
• a 15-bit mantissa. An implied bit to the left of the radix point is assumed, which is always 1, unless the number is zero itself, when the implied bit is 0.
Double
A double data type is 24 bits or 32 bits wide (selected during the compilation) and is used to store double-precision floating-point numbers. The truncated IEEE 754 24-bit format is used in 24-bit mode. The 32-bit format is based in the IEEE 754 32-bit standard where the number consists of:
• a 1-bit sign bit;
• an 8-bit exponent stored as excess 127;
• a 23-bit mantissa.
In the following example, the variable temp stores the number 12.34567 as a double-precision floating-point number:
