Create different arrays, and then determine if they are string scalars.

Test a string scalar.

str = "Mercury"

str = 
"Mercury"

tf = isStringScalar(str)

tf = logical
   1

Test a string array with multiple elements. Since str contains more than one element, isStringScalar returns 0.

str = ["Mercury","Gemini","Apollo"]

str = 1x3 string
    "Mercury"    "Gemini"    "Apollo"

tf = isStringScalar(str)

tf = logical
   0

Test a character vector. Since character vectors are not strings, isStringScalar returns 0.

chr = 'Pluto'

chr = 
'Pluto'

tf = isStringScalar(chr)

tf = logical
   0