The "IsKeyDown" function in "fx-9860G SDK Libraries" has been deprecated and is now
unsupported in "USB POWER GRAPHIC 2" version of "fx-9860GII(SD)",
"GRAPH75(95)" and "fx-9860G AU PLUS".
Instead of "IsKeyDown", please use "GetKey" or "Bkey_GetKeyWait"(new function)
according to the use cases illustrated below.
The following use cases are only examples, “GetKey” and “Bkey_GetKeyWait” are not
guaranteed to perform identically to “IsKeyDown”.


Case1: Poll key state until a particular key is pressed
・Code example (using "IsKeyDown")
while (1){
if (IsKeyDown(KEY_CHAR_0)) break;
}
・Code example (using "GetKey" instead of "IsKeyDown")
unsigned int key;
while (1){
GetKey(&key);
if (KEY_CHAR_0 == key) break;
}
Case2: Check to see if a key is pressed (with an optional wait/timeout)
・Code example (using "IsKeyDown")
int flag0 = 0;
if (IsKeyDown(KEY_CHAR_0))
flag0 = 1;
・Code example (using "Bkey_GetKeyWait" instead of "IsKeyDown")
int kcode1 = 0, kcode2 = 0, flag0 = 0;
short unused = 0;
if (Bkey_GetKeyWait(&kcode1, &kcode2, KEYWAIT_HALTOFF_TIMEROFF, 0,
1, &unused)==KEYREP_KEYEVENT) {
if ((kcode1==7)&&(kcode2==2)) flag0 = 1;
}
All the details in the attached pdf. Perhaps many games/applications will not work on new model fx-9860 USB POWER GRAPHIC 2

Source: Casio