Help in converting char/string

Using Arduino Programming Questions
1

hi sir/ma'am how to convert a char to a string?

i got this error.

sketch_aug27a:90: error: invalid conversion from 'char' to 'const char*'
sketch_aug27a:90: error: initializing argument 1 of 'String::String(const char*)'
sketch_aug27a:93: error: invalid conversion from 'char' to 'const char*'
sketch_aug27a:93: error: initializing argument 1 of 'unsigned char String::equals(const char*) const'

char x;
n[20];

if((x, n)>0) // Number, Number length
{
String num=x;
if(num.equals("12345")){
Serial.print("Ok");
}
else{
Serial.print("Done");
}

2

You have made many errors. You need to study more the C/C++ language, sorry.

  1. variable n need a type, for example
char n[20];
  1. if with x,n is wrong. no sense in this form.
if(x>sizeof(n))

to know if x is great of the size of array n

and use tag code for your sketch on post, see this section 7 else some part of code can not right visible.
http://forum.arduino.cc/index.php?topic=149014.0