is_set.l1.v = tstbit(byte_string.i1a.r, bit_number.i2.r)

	is_set.l1.v = tstbit_c(byte_string.i1a.r, bit_number.i4.v)

	This logical function tests a bit in a byte string.  It returns
	TRUE if the bit is set and FALSE otherwise.  "bit_number" must be
	an integer bit number ranging from 1 to 32767 with each bit
	being numbered in ascending order from right to left.

	byte_string	byte or array of bytes to test (up to 4096 bytes)
	bit_number	bit number (starts at 1)

	This function returns status values as follows:

	FORTAN_TRUE		requested bit is set
	FALSE			requested bit is clear

	This function requires the following include files:

	cnsparam_h, clib_h

	Related functions:

	bit_count_c, masked_off_bit_count_c, setbit(_c), rstbit(_c),
	bit_field_circular_shift_c, icshft

	C/C++ usage:

	char	is_set;
	char	byte_string[NUM_BYTES];
	int	bit_number = BIT_NUMBER;

	is_set = tstbit_c(byte_string,bit_number);