node.js: Path not being created using fs lib

No directory is created using fs.mkdirSync function - what's wrong here!?

var fs = require('fs')
const path = require('path');
fs.mkdirSync(path.join("c:","b"))
console.log(fs.existsSync(path.join("c:","b")))

Output is:

/temp/file.js:3
fs.mkdirSync(path.join("c:","b"))
   ^

Error: ENOENT: no such file or directory, mkdir 'c:/b'
    at Object.<anonymous> (/temp/file.js:3:4)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.runMain (module.js:605:10)
    at run (bootstrap_node.js:418:7)
    at startup (bootstrap_node.js:139:9)
    at bootstrap_node.js:533:3

Then i created a directory x in c:\ and executed the following

var fs = require('fs')
const path = require('path');
console.log(fs.existsSync(path.join("c:","x")))

but again got:

false

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