Post-conviction Procedure Act is a uniform law which provides that a person convicted of a crime and incarcerated under sentence of death or imprisonment may institute a proceeding under the Act to set aside or correct the sentence, which proceeding comprehends and takes the place of all other common-law and statutory remedies previously available and is to be used exclusively in lieu thereof. Under the Act one may institute proceeding if he claims that:
a. his sentence was imposed in violation of the United States Constitution or the Constitution or laws of the state;
b. the sentencing court had no jurisdiction;
c. the sentence exceeds the authorized maximum; or
d. the sentence is otherwise subject to collateral attack upon any ground of error previously available under a writ of habeas corpus or of coram nobis or other common-law or statutory remedy.