Scalar processor
Scalar processors represent a class of computer processors. A scalar processor processes only one data item at a time, with typical data items being integers or floating point numbers.

Classification 
A scalar processor is classified as a single instruction, single data (SISD) processor in Flynn's taxonomy. The Intel 486 is an example of a scalar processor.  It is to be contrasted with a vector processor where a single instruction operates simultaneously on multiple data items (and thus is referred to as a single instruction, multiple data (SIMD) processor). The difference is analogous to the difference between scalar and vector arithmetic.

The term scalar in computing dates to the 1970 and 1980s when vector processors were first introduced.  It was originally used to distinguish the older designs from the new vector processors.

Superscaler processor 
A superscalar processor (such as the Intel P5), on the other hand, may execute more than one instruction during a clock cycle by simultaneously dispatching multiple instructions to redundant functional units on the processor. Each functional unit is not a separate CPU core but an execution resource within a single CPU such as an arithmetic logic unit, a bit shifter, or a multiplier. The Cortex-M7, like many consumer CPUs today, is a superscalar processor.

Scalar data type 
A scalar data type, or just scalar, is any non-composite value.

Generally, all basic primitive data types are considered scalar:
 The boolean data type (bool)
 Numeric types (int, the floating point types float and double)
 Character types (char and string)

See also
 Instruction pipeline
 Parallel computing

References

Central processing unit