¶1This is a petition for habeas corpus challenging the calculation of the petitioner’s statu*125tory good time credits. The state has appealed from the judgment of the trial court ordering that these credits he calculated according to the law in effect at the time of the petitioner’s resentencing, General Statutes § 18-7a, rather than the law in effect at the time of his original sentencing, General Statutes § 18-7.
¶2The parties have stipulated to the following facts: The petitioner, Mark Moscone, was sentenced, on July 19, 1974, to a term of imprisonment of not less than nine years nor more than eighteen years for the crime of rape. Upon appeal to this court, the petitioner’s conviction was set aside and the case was remanded for a new trial. State v. Moscone, 171 Conn. 500, 370 A.2d 1030 (1976). Thereafter, the petitioner pleaded guilty to the same offense, and was, on April 12, 1977, resentenced to a term of imprisonment of not less than seven nor more than fourteen years. The defendant, John R. Manson, the commissioner of correction, has calculated the petitioner’s current sentence as if it had commenced on July 19, 1974, the date of the original sentence. The petitioner is entitled to additional statutory good time credits if his sentence is calculated according to the rules provided by General Statutes § 18-7a, whieh went into effect on October 1, 1976, after the date of his original sentence but prior to the date of his resentence.
¶3The governing statutes are, on the one hand, General Statutes §§ 18-7 and 18-7a, and, on the other hand, General Statutes § 53a-38. For present purposes, the two former sections are notable because they prescribe different formulae by which to calculate good time credit depending upon whether a *126prisoner was sentenced before or after October
¶4The issue raised by the present litigation is not § 53a-38’s provision of credits for time previously served, a provision which can readily be accommodated to either version of good time credits. Eather, the defendant commissioner argues that the opening words of § 53a-38 (c) require that, for all purposes, and not just in relation to time-served credits, a resentence “shall be calculated as if it had commenced at the time the vacated sentence *128commenced.” The trial court refused to accord so expansive a reading to § 53a-38, and we agree with its interpretation.
¶5It is true that, read literally, § 53a-38 appears to adopt an unconditional principle of relation back for all vacated sentences. It is also true that this court will not ordinarily construe a statute whose meaning is plain and unambiguous. Delevieleuse v. Manson, 184 Conn. 434, 438-39, 439 A.2d 1055 (1981); Frazier v. Manson, supra, 642; Evening Sentinel v. National Organization for Women, 168 Conn. 26, 29, 357 A.2d 498 (1975). This rule of statutory construction does not apply however if, as in this case, a literal reading places a statute in constitutional jeopardy. We are bound to assume that the legislature intended, in enacting a particular law, to achieve its purpose in a manner which is both effective and constitutional. Wagner v. Connecticut Personnel Appeal Board, 170 Conn. 668, 674, 368 A.2d 20 (1976); Whitfield v. Empire Mutual Ins. Co., 167 Conn. 499, 507-508, 356 A.2d 139 (1975); Amsel v. Brooks, 141 Conn. 288, 295, 106 A.2d 152, appeal dismissed, 348 U.S. 880, 75 S. Ct. 125, 99 L. Ed. 693 (1954).
¶6The constitutional problem posed by § 53a-38 (c), if read as the defendant commissioner proposes, is best illustrated by an examination of three factually related hypothetical cases. Assume that, on April 12,1977, three prisoners were sentenced to identical prison terms upon conviction of identical crimes. Prisoner A, if this is his initial conviction for this offense, is unaffected by § 53a-38 (c) and is entitled to good time calculated according to § 18-7a. Prisoner B’s case differs from that of prisoner A because prisoner B was previously sentenced under *129a conviction vacated upon appeal, has now been resentenced and has commenced serving his sentence. If prisoner B was admitted to bail, and therefore never taken into custody, during the time that his trial and his appeal were pending, then he too is unaffected by § 53a-38 (c) and entitled to good time calculated according to § 18-7a. This result follows from the conjunction of language in two subsections of § 53a-38. Under § 53a-38 (c), “the new sentence shall be calculated as if it had commenced at the time the vacated sentence commenced" (emphasis added), while under § 53a-38 (a), a sentence commences only “when the prisoner is received in the custody or institution to which he was sentenced.” Prisoner B, since his vacated sentence never commenced, does not fall within § 53a-38 (c). Prisoner B’s case is thus statutorily indistinguishable from that of prisoner A. Prisoner C’s case resembles that of prisoner B because he too was previously sentenced under a conviction subsequently vacated upon appeal. Prisoner C may, however, be subjected to different treatment, if he was incarcerated while his appeal was pending, because then he indeed did commence to serve the sentence subsequently vacated. According to the defendant commissioner, the fact that prisoner C commenced serving time necessarily invokes § 53a-38 (c), and that subsection ineluctably relegates prisoner C to good time credits calculated according to § 18-7 rather than § 18-7a. This result follows regardless of the reason for denial of bail to prisoner C. The prisoner who was financially able to delay incarceration pending appeal is, according to this construction of § 53a-38 (c), afforded more generous calculation of good time *130credits than is the prisoner who, for reasons of indigency, could not make bond.
¶7Just before the turn of the century, Anatole France commented on “the majestic equality of the laws, which forbid rich and poor alike to sleep under the bridges, to beg in the streets, and to steal their bread.” The Bed Lily, p. 95 (Stephens translation) (1896). Today, although poverty is not in and of itself a “suspect classification” for the purposes of the equal protection clauses of the federal and the state constitutions,
¶8In order to avoid constitutional difficulties, therefore, we construe § 53a-38 (c) as did the trial court, as anticipating the constitutional mandate of North Carolina v. Pearce. That case rests, the Supreme Court held, 395 U.S. at 721, “upon the premise that the original conviction has, at the defendant’s behest, been wholly nullified and the slate wiped clean.” The earlier sentence, now vacated, is void except that credit must be given under the new sentence for time served under the earlier one. Id., 718. Viewed from the perspective of North Carolina v. Pearce, the operative center of § 53a-38 (c) is its final clause that “time served . . . shall be credited,” and the earlier language is intended only to identify what prior time is eligible for the credit. In other words, to assure a prisoner the full credit for time served to which North Carolina v. Pearceconstitutionally entitles him, his sentence must be calculated to take into account “the time when the vacated sentence commenced” which is when the prisoner actually entered into custody under § 53a-38 (a).3
¶9Determination of statutory good time credits depends upon the date of a prisoner’s valid sentence in relation to the provisions of §§ 18-7 and 18-7a. We hold that the operative date of the petitioner’s sentence, under these statutes, was April 12, 1977. He is therefore entitled to good time credits calculated according to § 18-7a.
¶10There is no error.
¶11In this opinion Bogdahski, C. J., Parskey and Armentano, Js., concurred.
¶12General Statutes § 18-7 provides in part: “powers and duties OP WARDEN. PUNISHMENT AND REWARD OP INMATES. The warden shall manage the Conneetieut Correctional Institution, Somers, subject to the direction of the commissioner of correction, and he shall keep all the prisoners employed in such labor as the commissioner orders, during the term of their imprisonment. He shall also keep a record of any punishment inflicted upon a prisoner, showing its cause, mode and degree, and a like reeord of the conduct of each prisoner. Any prisoner may, by good conduct and obedience to the rules of said institution, earn a commutation or diminution of his sentence, as follows: Sixty days for each year, and pro rata for a part of a year, of a sentence which is not for more than five years; and ninety days for the sixth and each subsequent year, and pro rata for a part of a year, and, in addition thereto, five days for each month as a meritorious time service award which may be granted in the discretion of the warden and the commissioner for exemplary conduct and meritorious achievement; provided any serious act of misconduct or insubordination or persistent refusal to conform to institution regulations occurring at any time during his confinement in said prison shall subject the prisoner, at the discretion of the warden and the commissioner, to the loss of all or any portion of the time earned. Said commutation of sentence shall apply to any prisoner transferred from the Conneetieut Correctional Institution, Somers, to the Connecticut Correctional Institution, *127Cheshire. When any prisoner is held under more than one conviction, the several terms of imprisonment imposed thereunder shall be construed as one continuous term for the purpose of estimating the amount of commutation whieh he may earn under the provisions of this section. . . .”
¶13General Statutes § 18-7a provides: “good conduct credit for PRISONERS SENTENCED ON AND AFTER OCTOBER 1, 1976. Any person sentenced to a term of imprisonment, on and after October 1, 1976 and while still serving sueh sentence whether such sentence is for a definite, indefinite or indeterminate term, and regardless of the institution wherein the prisoner is confined may, by good conduct and obedience to the rules which have been established for the service of his sentence, earn a commutation or diminution Of his sentence in the amount of ten days for each month, and pro rata for a part of a month, of a sentence whieh is for not more than five years, and fifteen days for eaeh month, and pro rata for a part of a month, for the sixth and each subsequent year of a sentence of more than five years. In the case of an indeterminate sentence, such credit shall apply to both the minimum and maximum term. In the case of an indefinite sentence, such credit shall apply to the maximum term only. Any act of misconduct or refusal to obey the rules which have been established for the service of his sentence shall subject the prisoner to the loss of all or any portion of such credit by the commissioner or his designee.”
¶14For crimes committed after July I, 1981, § 18-7a (b) now provides a new and more limited calculation of good time credit.
¶15 U.S. Coast., amead. XIV § 1; Coaa. Coast., art. I § 20.
¶16 Although the record does not expressly indicate the petitioner's indigency, we can infer that fact from his continued legal representation by public defenders.
¶17 A closely parallel provision in the New York Penal Code, § 70.30.5, has been interpreted, in an attached commentary, as follows: “Subdivision 5 grants credit for time served . . . when a new sentence is imposed in its stead.”
¶18The Model Sentencing and Corrections Act (U.L.A. 1978) provides similarly, in § 3-502 (e) : “If a sentence is set aside and the offender is reprosecuted or resentenced for the same offense or for another offense based on the same conduct, he must be given credit against his new sentence for all time served pursuant to the prior sentence which has not been credited against another sentence.”
¶19Our research has turned up no instance of statutory linkage *132between, credit for time served and good time credit. In tbe Model Sentencing and Corrections Act, different types of credits are independently codified in different subsections of § 3-502.
¶20 We note that, in addition to separate good time credits, the legislature has provided presentence confinement credit and good conduct credit for time served “in a community correctional center” by a person who “was denied or was unable to obtain bail.” General Statutes §§ 18-98 and 18-98e.